Most women would rather be Elon's 3rd wife rather than the only wife of a Walmart shift manager.

If plural marriage ever becomes legal, it will have massive dysgenic consequences. Older men, the ones with the money, have lower quality sperm. Even if they are banging young hotties, this leads to a decline in the quality of the offspring.

Luckily, plural marriage isn't normal, nor are there that many billionaires with impregnation fetishes.

Lastly, without some sort of primogeniture, it wouldn't be long until you had some sort of violence issues.