The current status quo of serial monogamy and female promiscuity is de facto polygamy. Attractive men can and do have sex with dozens of women in their lifetimes, and they rarely have reason to commit to one woman for long periods of time, let alone to commit to multiple women at the same time. They're perfectly happy to exchange their genetic currency for casual sex and occasionally relationships, and that's all they care about. The last they'd want is to become providers for multiple foids.
Polygamous marriage is illegal because of its association with patriarchy and because most married women don't want to end up having to share the same resources and living space with "sister wives". If polygamous marriage were legalized in today's society where foids can divorce-rape their husbands, nothing would change, because the vast majority of married women would never allow their husbands to be polygamous.
