If you're going to Bob Jones University, you can be the Chadliest Chad that ever Chaded, but you're probably not going to get much or any casual sex, because the girls of BJU basically don't want casual sex. On the other hand, if you're around pink-haired poly bisexuals in San Francisco (to pick on my own demographic), all getting same-night lays requires is the skill of actually asking girls to have sex with you. (If you're part of their extended group of friends, anyway.)

I expect this pattern holds true across a variety of different social groups: people who like casual sex will tend to cluster in certain subcultures, while people who are averse to it will cluster in others. This implies that, for many people who want to have casual sex, changing social groups is lower-hanging fruit than becoming more attractive.