Feminists

because if you look at the overwhelming majority of cases, it's the mother that is most in charge of the children, and this applies to who takes off work to stay home with the kids, to who sits with them to do the homework, wipes their behinds 90% of the time, jumps up out of bed when they're crying, and knows (without looking it up) nearly everything that is going on with the children, from the kids' doctors, what issues the kids are experiencing in school, to everything else.

With exceptions (for example, bipolar, psychotic, mentally ill mothers, or mothers who state it out that they simply don't give a damn about the kids, or stay-at-home dads), that's the way it is. Judges (male and female) are not stupid, attorneys (male and female) are not stupid, and the population at large (male and female) is not stupid, and would never deny this.

I worked temporarily with a family law attorney, and the things I saw there were amazing. Divorce brings out all kinds of behaviors in people. I literally saw men seeking custody of the children who had no idea what the kids' teachers names were, what their birthdays were, and had never done one thing for the kids, but they wanted custody. Why? To be an ass, because of the financial issue (they felt the money that kids require is simply fun-money for the mom), and many other reasons which were ridiculous. It aggravated me, it aggravated the attorney I worked with (and he was male), but we represented these people and it was our unpleasant job to attempt to get custody for someone who had never before cared a whit about the kids.

So, why is custody generally given to the moms? That's why. Further, generally does not mean all the time. It means most of the time.