Time, Intimacy and Historical Societal Norms
It takes something like eighteen to twenty hours a week to establish and maintain an intimate relationship.
In line with that idea, some study found that getting married typically cost a person two friends. They simply didn't have enough hours in the day to keep up with five or more friends anymore.
The size of their inner circle dropped by ONE and also now included a spouse, so the existence of the spouse replaced someone. Thus, there were two fewer good friends in their life.
If you crunch the numbers, this fits with past cultural norms where a successful man could have a wife and a mistress so long as he was good to both of them and provided for both of them: There are enough hours in the week to work forty or more hours and have TWO genuinely intimate relationships.
The math quickly stops working if you move beyond that, though that would depend on some details. You can be close to a spouse AND the children because you all live together, so I imagine if you are Middle Eastern and have four wives and live with all of them, it's feasible to actually know them all well enough for them to all be genuine relationships.
But the Western historical pattern of living with one woman full-time and having a dish on the side as separate lives doesn't hold up if you try to add a third lover. There simply isn't enough time.
Theoretically, if you inherited vast wealth and could hire people to cook and clean while not having to work for a living, there's time enough for three or four intimate relationships with lovers, but then what do you talk about with them if there's no job and no hobbies? Your other lovers?
That fundamentally violates the concept of trust and intimacy most people have AND it means there's no there there. Who are you other than the fucktoy of too many people that you need to hide from polite society?
Part of the reason Western culture tolerated a wealthy man having both a wife AND a mistress back in the day before TV and YouTube and etc is because people understood you could actually get to know two people well and actually be good to both of them if you made enough money to provide housing for both and support any children that resulted.
And the world was different back then. You only really needed your inner circle to understand the situation, not your five million social media followers.
I think we no longer tolerate that in part because it's simply too hard to navigate the social stuff for successful people who typically have a relationship to the public and need public approval, in part because the public wants to know they can trust you and the world is too big for people to figure out if you're good to both your women or an asshole to both of them.
So they want a simple test: Are you involved in a faithful monogamous marriage?
If yes, we trust you. If no, we don't.
They can in theory judge if you are married and faithful. They can't judge your private relationships beyond that and it's too many variables.
They NEED to trust people in power. Politicians don't stay in power if the people don't trust them.
Unfortunately, it creates friction because one of the eats good men historically made things work was that if they got married, had kids and then weren't happy with the wife who was having too many "headaches" and no longer wanted to sleep with him, everyone was okay with him taking a mistress IF he was good to BOTH women.
So it was possible for him to both do his duty AND get his own needs met even if he learned only after there were kids that his wife really didn't want to sleep with him and was just after his money.
She could potentially still fulfill an important role in his life by being publicly presentable at various functions and he wasn't having the life sucked out of him.
My understanding is that about eighty percent of women pass on their genes and only fifty percent of men do. So there is a very long human history of men having children by TWO women and women only having children by one man.
Men seem to trend towards either being asexual or too much for one woman. And now the entire planet expects everyone to practice faithful monogamy.
And we wonder why it's all so amazingly broken.