They don't have to, they're just greedy and "need" to have a new BMW and Lexus every few years, live in fashionable neighborhoods in expensive metros, and have "important" jobs. You don't need that shit in Cleveland.
Not everyone is how they appear and your disregard and assumption of greed is just sad. For example, I'm going to college, working 'and' working on a side project. I face the near future prospect of having to support myself and two parents, which hardly requires greed on my part. This situation is far from uncommon.