Why are women classified as "caretakers" and men as "money makers"?

For the first few years of childhood, women offer things to their children that men simply can’t, such as breastmilk. Nowadays there are hundreds of formulas and things to replace what mothers a90re built to offer, making it possible for men to take over the child care responsibilities. However, these classifications have been around a long time, and I can only assume they stemmed partially from these motherly needs and responsibilities. Women were needed at home to take care of the children (mainly talking about the younger-agd children), and men needed to work to make money so that the women could have the supplies she needed to run the house and keep their children clothed/fed.