My cousin is a Family Law attorney out in Cali, I was talking to her last month about this. She's said that it's not something that no one is aware of within the institution of Family Law. In fact, things are actively being done to change it

For example, in the 90's, a woman had to be a drug-using, abusive hooker in order to not get majority custody if she asked for it...and once she had it, it would nearly take her dying for it to be revoked. Even IF she died, there's an even chance that her relatives would get the kids over the father.

But in the past decade, major changes have happened in that area, and now, there is nothing even close to that guarantee in place for women. These days, many districts will assign a counselor who will spend a bunch of time with both mom and dad, and that counselor will ideally make an informed decision based upon the best interest of the kid. The "mom as a default" rule is diminishing fast in that context. Further, dads are getting much more standing in court when it comes to contesting custody.

All of this is anecdotal, of course, and I'm sure there are anecdotes of districts who are still in the "woman gets it all" ideology. I personally have a friend who is in danger of losing her child, not because she is a bad mother...she's great. She has a lot of help from the family, she's not abusive, she's employed, she lives in a nice house in the suburbs. But the dad has convinced a counselor that he'd be better.

Again, it's all anecdote, except for one thing: The justice system KNOWS that it isn't fair, and many people are working to correct it in many places in the US.