Because all the great originals have either died or sold out, and the new music (including pop as well) has become all this auto-tune bullcrap about, well, nothing. Also the new beats fail in comparison to those of yesteryear (Bedrock has the kind of annoying overused lullaby beat I'm referring to).
let me guess, you're probably just under the impression that all rap is about guns, b*tches and weed. am i right? it's either that or you just listen to the crap on the radio, and even i think that mainstream rap is horrible. it's really easy to stereotype something you don't fully understand.