Some random thoughts:
Corporate influence has geared popular Hip Hop toward young/teenage children. Young/teenage children want to fit in, are easily influenced, and are mesmorized by nice cars, drugs and alcohol, nice clubs and nice clothes. This is mainly because young kids can't drive, can't drink, can't get in clubs, and don't have money to buy nice clothing. When they get older, they have new experiences. They worry less about fitting in. They aren't easily influenced. And by the time they reach adulthood, they are no longer mesmorized by nice cars, drugs, nice clubs, and nice clothes because they will experience that. In fact, as they get older they will probably begin gearing their income toward their children, and at that point the cycle of life repeats itself.
As people mature, the "Hip Hop" lifestyle becomes more comical and comical. Throwing hundreds of dollars at strippers, buying nice cars and rims, having a hat to match every oversized 6XL screenprint shirt you have, smoking weed with your boys in your car listening to your favorite artist like its a man date, saying YADADAMEAN and yelling ERRAY or Hey Yo Bitch Was Up at women doesn't take a person anywhere further than their block. So as people think for themselves and outgrow what they thought was cool, they choose their own direction.
In Hip Hop sales, what this has created in my opinion is less skilled and respected top artists, but very much appreciated and supremely skilled smaller artists like Techn9ne, Atmosphere, Immortal Technique, Devin the Dude, Jacka, etc. Hip Hop turns into fine wines or microbrews. Nobody older than 21 buys Budweiser anymore. Not when they can have Corona or Anchor Steam or a hefeweizen or something like that. So maybe Jacka and Atmosphere are both great artists to me, but maybe I like Corona AND Anchor Steam . They’re both good but they don’t appeal to everyone. So maybe you only like one of them. Mature consumers split their money between hundreds of up-and-coming or underground rappers. The young spend their money on what they see or hear, which is Budweiser. So Budweiser sells more than Corona and Anchor Steam, but that doesn’t mean the world forgets about having a good beer!