So you're saying that, in general, women have less of a desire for sex then men?

Historically, multiple women have been willing to share a single man with resources to provide for them and their children. Harems are common on other species (gorillas, lions and so on) and we can speculate that humans are flexible to this arrangement. That is not to say that it appeals to us the most intellectually/emotionally, but from survival of the species point of view, better a guy who can protect/feed/provide for all his children with multiple partners rather a physically meek / mentally unstable / low social status one who will have trouble providing for even his children with one woman.

Except that as humans we invented police, welfare and birth control, so now the hot/rich guy has less responsibilities and it can be just one night stands rather than having at least some concerns about upkeep of the harem/mistresses. And marginal guys no longer have an option of a discarded mistresses who has a child that needs at least some kind of support.

For some women, sure. But there have also been rare societies where the women had their pick of men, and the men were responsible for taking care of their sister's offspring, not their own.

Historically, also, some of those harem women were having fun with men who weren't their husband. This is also common in other species, with at least one species of old-world primate that I can't recall the name of having a sexual structure where the females, who are technically part of a harem of an alpha male, will have sex with other males with the alpha male's tacit knowledge, as long as it isn't in his face.

I am not super motivated to promote cheating with boss'es mistress as a replacement for porn and sex work. Even then, people are only motivated to cheat with someone fairly hot in the first place, so it doesn't solve the problem. "Find someone of your own caliber and stick with him/her" does for everyone except outliers, but not going to happen.

Plenty of married people cheat with prostitutes every day.

For some the thrill of the cheating is enough to make the partner seem more attractive than they physically are.