Boys are idiots. Girls are idiots, too, of course, but boys are a special kind of idiot.
A girl, for instance, will vote for a boy in an election, or go to a movie that's about a boy, or buy a book that features a boy hero (or villain). Boys are much less likely to return the favor. They can't wrap their feeble minds around the idea that this girl might have anything in common with them. It's like they can't recognize girls as human beings.