Because they still have innocence and purity which no female past the age of 12 ever actually has (no matter how hard or well they can act as if they do) along with a simpler, easygoing nature that again their older slut whore counterparts dichotomize. Because I mean, what's not to love about contralogical mind games and drama, right? On top of the rampant promiscuity, it shouldn't be any wonder why.