Trivia: When Hiro buys the comic book, he pays with a 1000 yen note, which is a typical price for manga in Japan. This translates into approximately $8.48 American. As a typical 2006 newsstand price for comics is about $2.99, the vendor actually got more than his money's worth.
Trivia: The date on Hiro's watch, October 2, is the same date this episode first aired in most North American areas.
Chosen answer: Because he's an idiot. From the story point of view, they needed the vault to actually be physically open so that the release of the virus would be a credible threat. Unfortunately, this required that Peter conveniently forget that he could simply walk through The Wall and use his telekinesis to tear the door open instead. Peter's increasingly large arsenal of abilities, where he ended up having pretty much any ability required for any situation, led to a situation where it became necessary to either have Peter apparently forget that he had a given power, as with the vault door scene, or become naively trusting, as with his refusal to scan Adam's mind to confirm his good intent. This problem, which simply made Peter look increasingly dumb as the show progressed, may well have been a key factor in the decision to severely reduce his ability during season three.
Tailkinker ★