Well.... part of the reason is because the variation in music is pretty much exhausted. The PIONEERS have already done their stuffs, thus they will always have a place in the history books.
Which also explains why today at jamming studios you can still hear bands doing covers of metallica, GnR (sweet child), Radiohead (creep), nirvana (smells like...), Deep Purple (smoke over water)...etc.
All these are ground breaking music, and will remain popular for a very long time. I see that few bands are doing (all the small tings). Cause these are just FAD tracks, but much later occasionally will still have some band will cover it.
This is the magic of music. Even the pop industry evolving, recently being hip hop.
Don't be sad, cause THERE IS NO SCHOOL LIKE OLD SCHOOL. Listen, promote and be proud.