Actually, polygamy was a response to excess females - as Muhammad's cohorts died off, he had their widows married to those who remained standing. The problem of excess females led to an ever-widening spiral of conquest for loot, as the men joining his army died, the remaining men had to take on the widows of the dead, thereby necessitating the acquisition of yet more loot. Note that the female surplus problem was severely aggravated by the practice of massacring male captives.
But once things stabilize after wars of conquest, as we have now, you have lots of excess low-status males at loose ends if you maintain a polygamous system.
Surely you’re not asserting that the reasons polygamy was adopted 100s of years ago in the Muslim world are still in play there today? They simply don’t have excess females.
And as you will surely admit, China very much has the opposite problem. And while it has occurred, polyandry is not common in history. At all.