If both partners work and get equal pay, then there is no alimony in the divorce. Usually, though, what happens is that the woman ends up in a lower-paying job, either because it has better hours for her to do childcare, or because she does part-time work so she can do childcare. This is a sacrifice in money that the family makes in order to have a parent spending more time with the children. The problem with it is that when a divorce occurs, it leaves the woman with the low-paying job, so now the sacrifice in money is purely on her side. Alimony is an attempt to correct that.