A aparição é extremamente difícil e muitos magos não fazem isso.

A aparição é uma das formas mais arriscadas de transporte mágico, mais do que vassouras ou pó de flúor. Aparatar carrega o risco de Splinching, e tanto a Aparição Regular quanto a Aparição Side-Along causam uma sensação desagradável nos feiticeiros sendo transportados desta maneira.

“They left half of themselves behind,’ said Mr Weasley, now spooning large amounts of treacle onto his porridge. ‘So, of course, they were stuck. Couldn’t move either way. Had to wait for the Accidental Magic Reversal Squad to sort them out. Meant a fair old bit of paperwork, I can tell you, what with the Muggles who spotted the body parts they’d left behind …’

Harry had a sudden vision of a pair of legs and an eyeball lying abandoned on the pavement of Privet Drive. ‘Were they OK?’ he asked, startled.

‘Oh yes,’ said Mr Weasley matter-of-factly. ‘But they got a heavy fine, and I don’t think they’ll be trying it again in a hurry. You don’t mess around with Apparition. There are plenty of adult wizards who don’t bother with it. Prefer brooms – slower, but safer.”
_{^{- Harry Potter and the Goblet of Fire, Chapter 6 (The Portkey)}}

Arthur Weasley descreve a Apparation como algo que não deve ser confundido, e diz que muitos bruxos preferem a segurança das vassouras. Presumivelmente, a maioria dos bruxos seriam ainda mais cuidadosos quando viajam com crianças menores de idade do que estariam sozinhos, então é provável que a maioria dos bruxos não arriscaria se arriscar com seus filhos ou filhos que eles cuidam. .

Harry aos dezesseis anos reage mal a Dumbledore transportando-o pela Aparição.

“Harry felt Dumbledore’s arm twist away from him and redoubled his grip: the next thing he knew, everything went black; he was being pressed very hard from all directions; he could not breathe, there were iron bands tightening around his chest; his eyeballs were being forced back into his head; his eardrums were being pushed deeper into his skull, and then – He gulped great lungfuls of cold night air and opened his streaming eyes. He felt as though he had just been forced through a very tight rubber tube. It was a few seconds before he realised that Privet Drive had vanished. He and Dumbledore were now standing in what appeared to be a deserted village square, in the centre of which stood an old war memorial and a few benches. His comprehension catching up with his senses, Harry realised that he had just Apparated for the first time in his life.”
_{^{- Harry Potter and the Half-Blood Prince, Chapter 4 (Horace Slughorn)}}

Dumbledore era um mago habilidoso o suficiente para não machucar acidentalmente Harry, e Harry tem idade suficiente para entender o que está acontecendo, mas Harry ainda não se sente particularmente bem depois de sua experiência aparatando. Harry diz que prefere as vassouras depois dessa experiência.

Além disso, Ron fica mal Splinched quando Hermione tenta Side-Along Apparate com ele.

“Splinched,’ said Hermione, her fingers already busy at Ron’s sleeve, where the blood was wettest and darkest.

Harry watched, horrified, as she tore open Ron’s shirt. He had always thought of Splinching as something comical, but this … his insides crawled unpleasantly as Hermione laid bare Ron’s upper arm, where a great chunk of flesh was missing, scooped cleanly away as though by a knife.”
_{^{- Harry Potter and the Deathly Hallows, Chapter 14 (The Thief)}}

Ron está com dor, falta de carne, e tem que ter dittany aplica-se às suas feridas. Nesse incidente em particular, eles precisavam escapar rapidamente, mas em situações menos terríveis, é fácil entender por que os bruxos não arriscariam que isso acontecesse.

Para as necessidades de transporte da família bruxa média, as vassouras provavelmente seriam suficientes, e vêm com menos risco e desconforto do que a Aparição.

Além disso, aparatar em algum lugar geralmente exige poder visualizar claramente esse lugar.

Os passos da Aparição tipicamente requerem que o mago seja capaz de imaginar claramente o lugar onde eles estão tentando aparatar. Primeiro eles têm que imaginar o destino deles.

“Step one: fix your mind firmly upon the desired destination,’ said Twycross. ‘In this case, the interior of your hoop. Kindly concentrate upon that destination now.”
_{^{- Harry Potter and the Half-Blood Prince, Chapter 18 (Birthday Surprises)}}

Então eles têm que se concentrar em tentar ocupar o espaço que estão imaginando.

“Step two,’ said Twycross, ‘focus your determination to occupy the visualised space! Let your yearning to enter it flood from your mind to every particle of your body!”
_{^{- Harry Potter and the Half-Blood Prince, Chapter 18 (Birthday Surprises)}}

Presumivelmente, então, eles podem não ser capazes de aparatar em algum lugar se não puderem visualizá-lo adequadamente. Então, por exemplo, bruxos que não foram ao estádio, a Copa Mundial de Quadribol foi realizada e não pode visualizar que não seria capaz de aparatar lá. No entanto, há casos em que assistentes parecem aparatar em algum lugar que nunca viram antes, como Bellatrix sendo capaz de aparatar para a casa de Snape, embora ela esteja surpresa por onde está e como parece, por isso nem sempre é necessário ter visitado anteriormente.

No entanto, não é ilegal transportar um assistente para menores de idade dessa maneira.

O Ministério recomenda isso como uma maneira de remover os bruxos menores de idade do perigo, o que eles não fariam se tivessem tornado isso ilegal.

“Review the security arrangements around your house, making sure that all family members are aware of emergency measures such as Shield and Disillusionment Charms and, in the case of under-age family members, Side-Along-Apparition.”
_{^{- Harry Potter and the Half-Blood Prince, Chapter 3 (Will and Won’t)}}

Além disso, Dumbledore transporta Harry desse jeito antes dos dezessete anos.

“You have not, of course, passed your Apparition test?’ he said.

‘No,’ said Harry. ‘I thought you had to be seventeen?’

‘You do,’ said Dumbledore. ‘So you will need to hold on to my arm very tightly. My left, if you don’t mind – as you have noticed, my wand arm is a little fragile at the moment.”
_{^{- Harry Potter and the Half-Blood Prince, Chapter 4 (Horace Slughorn)}}

Não, não é ilegal.

De um ministério do folheto mágico no Half Blood Prince:

Review the security arrangements around your house, making sure that all family members are aware of emergency measures such as Shield and disillusionment Charms, and, in the case of underage family members, Side-Along-Apparition
_{Harry Potter and the Half Blood Prince- Will And Won't}

Provavelmente é muito difícil.

1. O fato de o ministério multar as pessoas por fazê-lo ilegalmente, e você tem que passar por um teste depois de ter aulas para aparatar:

   “You have to pass a test to Apparate?” Harry asked.
   “Oh yes,” said Mr. Weasley, tucking the tickets safely into the back pocket of his jeans. “The Department of Magical Transportation had to fine a couple of people the other day for Apparating without a license. It’s not easy, apparition, and when it’s not done properly it can lead to nasty complications. This pair I’m talking about went and splinched themselves.”
   Everyone around the table except Harry winced.
   “Er — splinched ?” said Harry.
   “They left half of themselves behind,” said Mr. Weasley, ...
   “So, of course, they were stuck. Couldn’t move either way. Had to wait for the Accidental Magic Reversal Squad to sort them out...
   “Were they okay?” he asked, startled.
   “Oh yes,” said Mr. Weasley matter-of-factly. “But they got a heavy fine, and I don’t think they’ll be trying it again in a hurry. You don’t mess around with Apparition. There are plenty of adult wizards who don’t bother with it. Prefer brooms - slower, but safer.”
   _{Harry Potter and the Goblet of Fire- The Portkey}

2. As coisas podem dar muito errado -

   There was a horrible screech of pain and everybody looked around, terrified, to see Susan Bones of Hufflepuff wobbling in her hoop with her left leg still standing five feet away where she had started.
   ...
   Three lessons on, Apparition was proving as difficult as ever though a few more people had managed to Splinch themselves.
   _{Harry Potter and the Half Blood Prince- Birthday Surprises}
   
   "...Disarmed the bloke holding mine, and Disapparated. I didn’t do it so well, Splinched myself again" Ron held up his right hand to show two missing fingernails;
   _{Harry Potter and the Deathly Hallows- The Silver Doe}
   
   The moment his eyes fell upon Ron, all other concerns fled Harry’s mind, for blood drenched the whole of Ron’s left side and his face stood out, grayish-white, against the leaf-strewn earth...
   “What’s happened to him?”
   “Splinched,” said Hermione, her fingers already busy at Ron’s sleeve, where the blood was wettest and darkest. Harry watched, horrified, as she tore open Ron’s shirt. He had always thought of Splinching as something comical, but this...His insides crawled unpleasantly as Hermione laid bare Ron’s upper arm, where a great chunk of flesh was missing, scooped cleanly away as though by a knife.
   _{Harry Potter and the Deathly Hallows- The Thief}

Vou responder aos seus exemplos com contra-exemplos para provar por que eles precisam se preocupar.

Expresso de Hogwarts

Aparição em Hogwarts é proibida, então os pais só podem aparatar seus filhos em Hogsmeade. Depois disso, barcos e carruagens movidas a thestral ainda são necessárias. Imagine a multidão lá, as crianças e os pais tentando encontrar uma carruagem vazia ou barco.

As you may know, it is usually impossible to Apparate or Disapparate within Hogwarts. The headmaster has lifted this enchantment, purely within the Great Hall, for one hour, so as to enable you to practice. May I emphasize that you will not be able to Apparate outside the walls of this Hall, and that you would be unwise to try.

Harry Potter and The Half Blood Prince,Ch. 18 Birthday Surprises

Você ainda precisa de um método de transporte confiável para os nascidos-trouxas, que eles podem compreender dizendo "apenas leve seu filho para a estação de trem". Os nascidos-trouxas também não têm ninguém para aparatar na escola.

"Er -- I need to be at King's Cross tomorrow to -- to go to Hogwarts."

Harry Potter and The Philosopher's Stone, Ch. 6 The Journey From Platform Nine And Three-quarters

Os alunos também deixam suas malas no trem e são levados separadamente para a escola. Com os pais carregando malas ao lado das crianças, Hogwarts não pode organizar tal sistema.

"Please leave your luggage on the train, it will be taken to the school separately."

Harry Potter and The Philosopher's Stone, Ch. 6 The Journey From Platform Nine And Three-quarters

Floo

Você não pode Floo em Hogwarts (Umbridge tinha privilégio). Acontece que você pode usar o Flu em Hogwarts, que é outra razão para não usar Apparition. Floo é usado principalmente para vir ao ministério. Enquanto um estudante médio não precisa visitar o ministério de vez, a aparição ainda é algo difícil de fazer para adultos. Outras respostas explicam essa parte claramente.

Carros voadores

Ninguém realmente se incomoda com carros voadores. Isso é puro Arthur Weasley .

Extra: Vassouras

“How’re we getting — wherever we’re going?” Harry asked.
“Brooms,” said Lupin. “Only way. You’re too young to Apparate, they’ll be watching the Floo Network, and it’s more than our life’s worth to set up an unauthorized Portkey.”

No final, acredito que o Hogwarts Express e o Floo são muito mais confiáveis do que o Apparition. Tanto para o transportador quanto para o transportado.