Why are grown guys 18 + chasing after girls 12-17?

Is this some type of sick thrill for them? I don't understand why do these grown men 18 and older chase after these little girls? I am pretty sure they can find some one there age and there are plenty of promiscuous college ladies,well just basically theres plenty of promiscuous women out here they can fool around with , but yet they want to p by all of them and get and underage girl. Can someone explain to me why?