They don’t, only upper middle class people do. And virtually all of them are liberal. And liberals almost always are drawn to hurting themselves in the name of virtue. It goes back to the penitents of 14th century Germany who would flog themselves walking along the streets in order to appease god. I never realized that this was so until I experienced life in a place where people don’t have this inclination at all. This concept of self inflicted pain being good for ones self is at the core of why liberal people are usually upper middle class. It promotes success and excellence. But it is so deep that most people don’t even realize they have it.