There is a reason for one man one wife, because it makes relationships possible.
If you want a sex machine, where you are a commodity on a relationship belt, most people over time would say get lost.
Families with over 3 children start to be a crowd or even a community not just a family.
If life is brute survival, and you grab what you can while you can, then this kind of behaviour makes sense. Once you go for multiple wives, whose wife is it anyway.
What about women with multiple husbands? Why not? There are very few cultures were this is the preferred option.
In some cultures what in reality this becomes is man and wife + x number of mistresses or affairs on the side, or what people call an open marriage.
People are using the wrong framework. Social behaviour is a particular way because it works, not because it is dictated.
As soon as std's become a major problem with no cures, suddenly behaviour and attitudes change.
Sin leads to death. Without modern medicine it is very easy to talk about rights of individuals to behave as they like. Would you marry a partner with a 90% chance they will kill you because of what they carry?
Anyone who thinks they can run a family with more than one wife and one husband needs counselling.