I wonder whether this was true in the pre-industrial world. If you work on a farm, or are apprenticed to your parents in a craft, both parents are probably going to be home most of the time, and the kids are going to be working along side them. So maybe we can blame this on Capitalism. Lots of other things wrong with the pre-industrial model though, like it's difficult for the kids to go to school, and so they usually don't learn to read.