Breastfeeding is a necessary part of taking care of a newborn that men cannot do. Women can do all the parts that you listed, plus the vital component of breastfeed. Hence, it makes sense to encourage moms to stay home with babies. Dads should stay home too, because the ideal is for mom and dad to be at home playing with babies (isn't that everyone's dream??). However, most people are not independently wealthy, so compromises are made, and dad goes to work.