I had my first, first hand experience with this in the early 70s. My wife's friend had two children, no father present, my wife agreed to keep her kids (No charge) while she went to work at Hardees, just until she "got back on her feet".
Within a month she quit the job, telling my wife that she could make more by not working. I didn't get it at first but then she explained all the "benefits" she lost by working and I got it. She was better off not working, even if she didn't have to pay a baby sitter out of her wages.
That was 40 plus years ago, it has only gotten worse since.
When my children were small I didn’t work, because I figured out having to pay someone to watch them; at that time there was no such thing as childcare, plus the cost of transportation going back and forth to work for the little money they offered wasn’t worth it. Another thing is the marriage penalty when both couples work