Maintaining a household really is at least a full time job. If you have a two income household, all that work still has to be done, so you go to work and then come home to a second job. Making the second job the full time job of the other person means each person now has an extra 20 hours a week. You could spend 10 hours a week at a social club and still be spending more time with your kids than you do now.
Meanwhile the money from the second job gets eaten up by commuting and childcare costs etc., and being thrust into a higher tax bracket, but also from having to outbid other two income households for artificially scarce housing in good school districts, which you can't avoid by not doing it yourself and so it's prisoner's dilemma. The two income trap is a real thing.