[ars]

Even when permitted it was very rare.

For one thing only the very wealthy could afford it - each wife was required to have her own house (separate rooms in one house was not enough).

For the most part it was practiced mainly by traveling businessmen/salesmen who would have a wife in each city where they worked. (Don't forget how slow and long travel used to be.)

The main reason for permitting it is that historically males died more often than females, so there is a small surplus of females, and permitting a small amount of polygamy helps with that.

It's no longer relevant these days.

[xerophyte12932]

As an insurance student, let me just point out male mortality is still considered higher than female mortality (hence higher premium rates for men). Though i have no numbers if the world has more females than males right now

[eru]

There's female infanticide and gender-biased abortions to more than balance higher male mortality in lots of the world.