Porque não se pode tirar nada do chapéu
According to Dumbledore, speaking of the Sword of Gryffindor,
Dumbledore reached across to Professor McGonagall’s desk, picked up the blood-stained silver sword, and handed it to Harry. Dully, Harry turned it over, the rubies blazing in the firelight. And then he saw the name engraved just below the hilt.
Godric Gryffindor
“Only a true Gryffindor could have pulled that out of the hat, Harry,” said Dumbledore simply.
—Harry Potter and the Chamber of Secrets
Para extrair qualquer coisa do chapéu, supõe-se que alguma outra condição tenha que ser atendida.
No entanto, tanto a espada quanto o Chapéu pertenciam à Grifinória.
Twas Gryffindor who found the way,
He whipped me off his head
The founders put some brains in me
So I could choose instead!
—Harry Potter and the Goblet of Fire
É provável que esta seja a causa de sua conexão, e que uma verdadeira Corvinal (por exemplo) não possa tirar o diadema do chapéu.