I know few people who are 30+ who don't associate rap with gangs & things and make assumptions about people's personalities based on the music. And again, I grew up in the genre. It still has its labels, and rappers like Chance, Kendrick, Cole, Kanye, throughout their career they talk about it in their music and outside during interviews.

The thing about rock is it evolved in pretty obvious ways through it's inception through Classic, Pop, Alternative, Punk, & Metal. Hip-hop became rap and as much as their are new waves of styles it hasn't had the same major shifts - so again that stereotype hasn't had any momentum to be swayed. Like people still think metal & pop are these black & white, dogmatic genres which evolved from rock and that's been around even longer than Rap.

So to me 30 years isn't enough time to make the argument that people should be used to it. Sure, people know it exists and it's mainstream but they still are closed off from it and generalize it based on the media's sensationalism.