That is a bit cliché isn't it? According to INSEE in France 12% of the kids were in shared custody and that is the mean. At 10 y old it is around 15%. And around 24% of the fathers get full custody.

So while there is a bias towards mother custody of the kids (around 2/3), there is still 1/3 of the kids where it is not the case.

Also, not having full custody of kids doesn't mean the father is leaving completely from the kids life. More often than not the kids need to stay with one parent because job and cost of living forces them to be more regionally apart (only 37% of kids living in same town). That doesn't mean the father do not see the kids in the weekends/holidays nor contribute financially to study.

So the reality is way more nuanced than you make it out to be in a small comment.