As much as it is a music thing, it's a cultural thing as well.
Back in the day, regardless of personal backgroung, social/economic situation, location, etc..many share the common experience of rolling the seeds and stems into the spine of "Physical Graffiti" while listening to Zeppelin, Floyd, Jimi, Carlos, Sabbath, The Dead, The Beatles, The Stones, Tull, Steely Dan, Bad Co., The Who...You know the bands, you know the songs. And even if not always the deepest cuts, much of the good stuff was played on the radio...coast to coast and around the world. A cultural identity so strong that despite being decades old (an epoch for pop culture), it still influences today.
Today, I belive that cultural experiences are more fractured. There is little shared experiences. Radio is dead. Music, regardless of taste, does not have the girth it once did. There are no more album covers...Hell, there aren't even any more seeds and stems.
Music today is downloaded, often after being turned onto by a friend, or streamed from an endless number of sources and listened to by individuals or a small group of the like minded and not by the masses on radio. That common cultural experience and influence ends at that circle of friends and sub-sub-culture.
A group of "seasoned" musicians can get together, someone can shout out a song ("Black Magic Woman" anyone?), guitarists will make sure they have the chord changes down, bass players and drummers will fake it until they're grooving, and just that quickly, they're all jamming on a GREAT song that has stood the test of time. I just don't think that there is enough common experience amongst younger musicians with contemporary music for this to happen.
My point is that the long shadow (and getting longer) of the deeper experience that many of us shared yesterday has a stronger influence than the shallower experience that nobody shares today.