Hotter take: men don't want long-term partners period, monogamy is social conditioning because it leads to stable and more successful settlements.
2) Most men are not capable of being promiscuous, even if they want to be
Also, part of the allure of promiscuity is being able to attract/seduce multiple women. Paying for sex eliminates that.
Genghis Khan had 6 long-term wives. Most likely, the women were forced to be monogamous, while he obviously wasn't.
Don't some behaviors like that also happen amongst other mammals or other animals in general?