This thread is def at risk to blow up lol but to answer your question Ree a big part of hip hop/rap culture (which is predominantly a black subculture) has been showing off all the materials/resources you have in comparison to other competing males to show dominance and success as a man. Thus showing off materials/resources became vogue as a means of publicly displaying their status.
Definitely an aspect of attention seeking which could be a byproduct of growing up in a rough situation causing low self esteem and a desire to be noticed/appreciated.
I was always interested in black inner city and hiphop/rap culture growing up and had a lot of friends immersed in it and its typically the "hot boy" cocky guys that engage in this type of behavior. Plenty of black ppl ingrained in rap/hiphop innercity culture that are very humble and maybe only wear a modest chain or rims on their car.
Money = status in black innercity of the US so by flashing how much money you've gathered you thereby indicate how high status you are (status getting you more respect, women, etc.)
That's minority, me is a minority.