Couple random points:
1. Rock is way more diverse than hip hop. Thats one thing hip hop needs is more divisions. Folk rock, Indie music, Metal. There are stars in all those genres who have been working for 10 years and never been famous. Hip Hop really only has one lane that every artist has to try to make it in if they want to eat...
2. Rock music in the mainstream is dead. Deader than hip hop. They can't make stars or hits and when they do the band disappears almost immediately. So at the moment its very "fickle". Like whatever happened to Kings of Leon?
3. Rock radio stations play mostly old songs, hip hop radio stations play mostly new songs.
4. The live show is not that important in hip hop. But thats the best and most reliable way for any musician have a career...
I was with you until you brought up Kings of leon, the album Come Around Sundown was very successful actually