that’s kinda the point, they aren’t flaunting their wealth exactly, they wouldn’t post their investment portfolio to look cool. “look guys, i’m investing my money optimally!”. what’s cool in the rap world is the implication of having large sums of cash, it suggests that they either got it through some cool way or are buying something cool. there’s also a kind of uncaring attitude, yeah they’re not investing it, and it shows that they get enough money to not really care