Porque Sidious não a queria morta na época. Ele precisava que ela assinasse o tratado.
De o script para o episódio 1:
Primeiro em uma cena inicial, o capitão Panaka percebe que a rainha corre o risco de ser sequestrada.
CAPT. PANAKA : They need her to sign a treaty to make this invasion of theirs legal. They can't afford to kill her.
Após o sequestro falhar, Sidious discute o fato de que ele precisa dela viva.
DARTH SIDIOUS : Destroy all high-ranking officials, Viceroy ...slowly...quietly. And Queen Amidala, has she signed the treaty?
NUTE : She has disappeared, My Lord. One Naboo cruiser got pat the blockade.
DARTH SIDIOUS : Viceroy, find her! I want that treaty signed.
NUTE : My Lord, it's impossible to locate the ship. It's out of our range.
DARTH SIDIOUS : ...not for a Sith...
A second SITH LORD appears behind DARTH SIDIOUS.
DARTH SIDIOUS : (Cont'd) ...Viceroy, this is my apprentice. Lord Maul. He will find your lost ship.
Uma vez que Amidala tenha superado sua utilidade (episódio 2), um caçador de recompensas é enviado para matá-la.
Sobre especificamente por que Sidious escolheu enviar Maul em vez de um caçador de recompensas para sequestrá-la, isso nunca é explicado no filme, mas a conversa de Sidious e Maul implica que revelar a existência dos Sith é parte do plano de Sidious.DARTH SIDIOUS : Move against the Jedi first...you will then have no difficulty taking the Queen back to Naboo, where she will sign the treaty.
DARTH MAUL : At last we will reveal ourselves to the Jedi. At last we will have revenge.
DARTH SIDIOUS : You have been well trained, my young apprentice, they will be no match for you. It is too late for them to stop us now. Everything is going as planned. The Republic will soon be in my command.