PM, you no doubt know that Shulchan Aruch says that a woman who doesn’t wear makeup according to the norms of her place can be divorced without a kesuva. Now of course, the husband can be mochel if he wants.
However, the down side is that what if he is later strolling down the street and sees all the other women wearing gorgeous makeup, and his wife looks very plain. He may either start to look at other women, or may subconsciously start getting upset with his wife that she doesn’t measure up, either of which is bad for shalom bayis.
Note that there is a story about the wife of reb Aryeh Levin who always said she was jealous of the zchus of a particular woman. This woman would put on her finest and get all dressed up to go out and greet her husband every day on the way home from work. She would wait on the corner for him to arrive.