I found this question on Quora.
Here’s my answer:
Equality would fix this. First, it’s important to note that this has changed dramatically in the modern era. Fathers get primary custody very often now.
Still, due to the inequalities that remain, mothers are often the primary care takers of their children. When a court needs to determine with whom to place children in a divorce, it often opts for the primary care taker.
If 50% of heterosexual divorces were ones in which the father was the primary care taker, almost all of those would lead to the father taking primary custody of the children.
Equality is equality for all. It’s often hard to notice the ways in which inequalities for women today translate into inequalities for men later. You found one such way. And when you follow it to the source, you can see that it is the inequality against women that is the problem here. A lot of inequality is like that.