One of the main reasons is that most of the bands that are now either disbanded or are making CDs now that aren't as good as their first ones were formed in the 80s. Metallica was created and definitely got their "Metal gods" status during that time. Megadeth, for the "disbanded" part... And a lot of other bands that broke grounds with their first or second album but are now just recycling their same **** over and over.
The best music out is not on the radio or MTV!!!