Both men and women used to wear makeup regularly. Why did men stop and not women? I mean "beauty enhancement" makeup not visual fx, war paint and the like. I'm specifically thinking about nobility in the 18th and 19th centuries.
Not a historian, I just want to push back a bit on that question. Makeup in the past was more of a luxury compared to the commodity that it's become today. You need to frame what era you want to compare in order to ask what changed.
Further many dyes and pigments in the past didn't match human skin tone, so you saw more face art as a custom of dress, spiritual garb, war dress, etc. Rather than beautifying through the improvement of complexion.
In aggregate, working class people, especially men didn't have an incentive to dress themselves up with beauty makeup any more in the past than today. So if you thinking about the trends of past nobles compared to working class people today, that is an assymetric comparison.
If you elaborate your question, I think there would be more to respond to. But such a general assertion does not coincide with our history in the general.