[jseban]

Because of the biological asymmetry between the sexes. A man can have thousands of children, and women can only have a small amount. It's what drives natural selection and evolution of the species. Some part of the men are supposed to get rejected.

[eftychis]

I know this will be hard to swallow for a lot: No polygamy is not stable and that is why it is outlawed in a lot of countries. Consider that men physiologically have a drive to produce wealth and "grow" to attract and sustain a family. (Nations I hear want that.)

What do you think throughout history the men that could not find a match did? They joined wars, became vagabonds, thieves, joined piracy or similar and went to forcefully acquire wealth and/or women (and rape). Needless to say a peaceful nation does not want that. Men are going to fight the rejection tooth and nail (a trait evolved in a similar fashion).

[whichfawkes]

I tend to agree with you that nations are essentially trying to optimize for wealth under their jurisdiction, but I don't think that _necessarily_ tells you anything about how they'll treat polygyny.