Making hip hop takes less work.
I have been a musician since age 14. And, it's a lot of work putting on your own shows.
By the end of booking the gig, getting everyone to the gig, driving thru heavy traffic and sometimes bad weather, setting up all of the equipment (drums, guitars, PA, monitors, etc.), doing a sound check.......you don't feel like doing sh/yt.
Maybe that is why most bands come off as in bad moods when the fans talk to them. All of the work that goes into being in a rock band is extremely demotivating and uninspiring.
With hip hop, it's easy. You set up a few things and you are ready to go. More time to talk to the fans, more time to "party" and less headache and time spent setting everything up.
Maybe that is why.
Or maybe hip hop is known for bringing the party, when rock is getting outdated and boring to the new generation.