We like youth, but not prepubescent

I'm curious about something. Most child molestation is "men who have sex with men". In many or maybe all of those cases, the boy is prepubescent. But heterosexual child molestation is often a highschool teacher and a student, or some middle aged man and a girl who lies about her age and says she's 21 to get into a club. It seems like two very different things.