Shouldn't men be the ones wearing makeup, dressing up, tanning, dieting, etc.?

You have to take into consideration that it's different for humans because women are after men's money so they have to place a lot of emphasis on their appearance. If men were after women's money then men would be the ones who have to place a lot of emphasis on their appearance. Women don't get all dolled up for nothing they do it in order to attract the man with the fattest wallet.