Well, that's a pretty broad generalization. Maybe, why do rappers, would be more accurate.
Why? It's tough for me to think on that same sub IQ level, but I'd assume it's about proving something. Most their lives they never had much, now they have a few dollars, so it shows some kind of "success". Really, it just shows how low class and low income go very well together.
Have we found a fourth part to Croatch's personality? Can we look forward to rappers, video's/protein shakes, fake DD's, and natty BBing being part of future Croatch posts?
In the case of the rappers, I agree with Croatch though.
The money, cars, and the like; are all part of the mentality that "I've made it." Growing up in a ghetto with nothing nice to speak of, and having only family to fall back on. Your job sucks, the money you earn sucks, you may/may not do drugs or be a dealer and you're constantly watching your back. Not a good way to live. Then you have a hit "record" and have all the money in the world. I'd be showing off too.
For others, they know no other way. They grow up watching their parents do the same thing, so they think it's right because that's all they see and assume there's one way to do it. They don't go out and earn their money the right way, they don't know how to act or whatever the case may be.
Fortunately, I've never had to live that life.