Ask HN: "Social Class" or "Purchasing Power" criteria for target ads?

Any ideas why FB, Google and Twitter don't target ads using the "social class" or "purchasing power" criteria? Anyone knows if they have tried something similar?

Since the early theories of marketing, we know that the "social class" of a person is an important type of market segmentation. In practice, by knowing how much money a person can spend, companies can target specific products or services to increase the possibilities of conversion. The theory seems easy, but I don't see companies using it online.

By the way, I don't think that the usage of the term "social class" sounds good. Despite being very popular, researchers and theorists do not come into consensus on its definition. I prefer "Purchasing Power".