you also have to put into perspective- alot of that music isnt really that old when you think about it..The music some of them listen to now is so drastically different than the music from the 80s and 90s that they just can't relate. It's like it's a totally different form of music. It's a much larger transition in sound than it was between the 80s and 90s sound. But that's just SOME of the contemporary music. You can still find contemporary Hip Hop music and artists that are akin to the music and artists of the 80s and 90s and the fans of that sound usually have no issue listening to older Hip Hop music.
outside of popular acts/songs- we werent up on alot of really good music from the late 60s-70s.. in the late 80s-90s.. i wasnt really checking for alot of say, Herbie Hancock & The Headhunters until late 90s, honestly.. just takes time for things to come full-swing..