Parents are too afraid to let their kids fuck up. I see helicopter parents like this all the time, and I think it has a profoundly negative effect on the kids. Of my friends from high school, the ones with overbearing parents just went crazy after high school. They ended up dropping out of college or having some sort of significant existential crisis, as they didn't really know how to deal with life in an independent manner. The best way to learn is to make mistakes. There's also no better time to make mistakes than when you're a kid, because you just don't have that many responsibilities...and the only real ramification is that you might get a stern talking to from your parents or get grounded. But instead parents are focuses on preventing any mistakes in the first place, which stifles any growing up that is supposed to happen.
Yeah, I see where you're coming from (and it's true that the kids who go crazy in high school get it together for college -- I know; I'm one of them). But it's important to remember that we're dealing with a 13-year-old kid who probably doesn't need a phone anyway, and also that it's a goddamn privilege. You can make the argument that having them sign a contract is just being pragmatic and imparting a life lesson of another sort: when you live independently, you damn well better be ready to honor contracts to landlords, bursars, the telephone company and everything in between.
I would argue that a 13 year old is old enough to know right from wrong. And you're right he probably doesn't need a phone, much less an iPhone, so either 1) Don't give him such a privilege or 2) Trust his judgement. Meddling about and choosing something between 1 and 2 is not healthy.