Discussions about hypergamy and Pareto principle and Alpha fucks/Beta Bucks is very common in online dating discussions. People definitely want to date the most attractive partner and it is very easy for even average-looking women nowadays to find many admirers. My question however, is if hypergamy is even a little bit true, why do most women in western countries support monogamy over polygyny?

Polygamy and harems are associated with wealthy Asian kings of the past who had an entire dungeons full of slaves or with strange patriarchal cults where old men abused multiple girls. But when you think about it from a pure logic perspective, polygyny benefits far more women than men. Only the most elite, top 5% of men, true alpha males, rich dudes, and gigachads have all the means to attract and support multiple women and any offspring. Those type of men already have tons of sex, but in a polygynous society, they will just benefit even more. In a polygynous society, average women who would otherwise have to choose with either dating an average dude or staying single can instead be an intimate partner and parent with one of the most powerful men in their society. Polygyny allows millions of women to fulfill their dreams of marrying and having kids with their favorite celebrity (only they have to share him).

Average men on the other hand, get completely screwed in a polygynous society. With so many women in harems, the only women average dudes would have access to at best is bottom-tier women that not even the alphas want. In a polygynous society, there isn't much difference between being a 1/10 man and being a 5/10 man.

So overall, a polygynous society is a society that benefits the average woman and fucks over the average man. This seems par for the course in modern western society, but there is surprisingly little support for this system even for the main beneficiaires? Why is that? Is it due to jealousy? Cultural/ethical/religious beliefs? Irrationality? Are decision-makers actually worried what would happen if there are millions of unmarried, unhappy men in their society? Or is there something I'm missing?