Ben and May divorced before Peter's parents died, so when Ben is murdered Peter goes into foster care. It takes just a tiny taste of superpowers for Peter to decide he doesn't want to put up with his horrible foster father anymore—the streets are infinitely more appealing. All he wants is to be Spider-Man anyway.
So he leaves.
Simple.
Simple, that is, until Iron Man needs Spider-Man's help. Peter isn't about to turn down an opportunity to fight alongside Tony Freaking Stark, but he also isn't going to let his hero know that his recruit is a fifteen-year-old homeless dropout. So they strike a deal. Peter will help Tony. In return, the mask stays on.
