Nearly 3/4 of American adults are in relatively stable monogamous (in theory, of course) cohabiting relationships including marriage. And that's not counting non-cohabiting relationships or casual sex at all.

Extremely promiscuous straight men are a tiny, tiny fraction of the population, and the extent to which they monopolize female attention is vastly exaggerated. If you look at India and China, where there's a genuine difference in the number of men and women in the population, you'll see all sorts of weird social effects that we just don't have in the US. True, some of that is due to general attitudes towards women, but some of it isn't.