There is a kind of desperate need for somebody to tell everyone what to do, which I find really peculiar in America. And then when you tell them, they're not interested, because it's also a country where everybody's opinion is their opinion, and they really don't give a damn what you think. So it's a very odd experience.
Asking why rappers always talk about their stuff is like asking why Milton is forever listing the attributes of heavenly armies. Because boasting is a formal condition of the epic form. And those taught that they deserve nothing rightly enjoy it when they succeed in terms the culture understands.