Where Do the Extra Men Go?

I have a question my brain is not large enough  to answer and so perhaps one of you Cappy Cappites can answer this for me.

In polygamous societies you have one guy with multiple wives.  Let's just say 4 wives to keep the math simple.

By default then, this means 75% of the men are WITHOUT wives/girlfriends.

So what do they do?

Originally I asked this about polygamous societies in general, however a friend of mine pointed out that in Mormonism it wasn't so much "just because they could do it," but rather the demands of early western pioneer life were so harsh and dangerous a lot of men didn't make it back.  This then resulted in one man taking on the role of father/husband to multiple children/women.

OK, granted, got that.  The other 75% of the men are dead.  But then I talked to my buddy Khanh and his dad has 8 mistresses on top of his wife.

Now, Vietnam, communist as it may have been, is not the wild west and is already settled.  So it isn't like there's a ton of Vietnamese guys getting knocked off leaving one poor guy to deal with 9 women.  ie-there is a surplus of men.  Throw in the overlap of Asian countries having a tendency to prefer males and selectively abort/abandon/kill females, there's even more of a numerical surplus (not just one dominant alpha male keeping 9 females off the market).

So again, what do the surplus of guys without women do?

Or is it that mistresses still sleep around and aren't really loyal to their sugar daddy?

I'm not trying to be off color, just curious if anybody knows more about this than me.