If I were to guess, I would say that it wasn't in His plan at the time to change the societal structure to that degree (it would have been pretty massive considering how the times with it being a male-dominated society). He knew the right timing and way of everything; of course now we can look back thousands of years later and wonder why He didn't change this or that right then and there. A lot of "better things" have improved for cultures and societies over time that weren't changed in the bible, but I doubt it meant it met God's father.
I think it's simply a case of men in power having multiple wives because they were seen more as possessions of a sort, "helpers" to bring children, cook, clean, and do other wifely duties. I don't fully back some of the studies that "show" it's based on the male being the decider of the gender of the child (it's a theory, not a proven fact, and there's studies that also show otherwise), so I doubt that had anything to do with it gender wise as mentioned in the thread. It's been shown that through hard times, mainly with loss of food or food choices, that more men are born during these time periods, so if more men were born during this time, it wouldn't be only down to the men chosen to have multiple wives. Here's one
article on that, which does assume men's dna can play a role, but mainly backs the theory on it being the diet of women and the food options/times that seem to dictate boy vs. girl births. The evolutionary reasoning behind this makes sense too.
Since men were considered the part of the family primarily paid attention to (with possessions, power, rights, reputation), it would make sense that those who were higher up would be entrusted with more wives to be responsible for.
And as Ignatius stated, a lot of it was logic and protection of the family line. Women would often die in childbirth, as would infants, so having more than one made more sense to carry on the family name. Cold sounding but reality. Men could spread plenty of the seed but they didn't actually have to have the dangers (or time maintenance) of the harvesting, so could it couldn't have worked the other way as effectively, even if it weren't such a male-dominated society.