Why do the boys just go after the popular girls?

They know she is "baaaadd" and has all the right moves in all the right places. It depends on your age group. If you are older, perhaps in high school, it could just mean that they know that they can have sex with her, that she is easy. If you are in let's say, Middle School, it could be it is because they know that she is "the it girl" despite her physical appearance and personality. They might just want her for the reputation. Guys can be so confusing, I know.