Why do guys (supposedly) prefer blondes?

Now I'm not a guy but I am bisexual, and with the whole big deal about blondes I can tell you that I've never been attracted to a blonde (save for one, but it was all natural and it was dirty blonde anyways). Brunettes are so much more sultry, and besides, blondes always either look too childish, too trashy, or too uptight. Brunettes on the other hand are just plain hot. Skin color and eye color doesn't really matter, but I love girls with dark brown hair. And btw, this is aside from personality, because obviously that comes first, I'm just talking pure sexual attraction. The worst however, is them fake blondes with their roots showing and their hair feeling like straw. I love shiny, soft, chesnut brown hair but I can't stand crunchy, brittle, yellow strands. I've always thought celebs like jessica simpson and pam anderson were fake and butt ugly but I think angelina jolie and mila kunis are amazing.