Currently, all the master copies of the episodes from the original run are being held by the Rock & Roll Hall of Fame. They were donated by Tad Low, the creator of the show. Although master copies are known to exist, they are not publicly available due to licensing. […] With the sheer number of episodes produced, the fact that both runs of the show are no longer rerun on VH1 or MTV Classic, and the fact that the show did not receive many home media releases (apart from a 1999 80’s-themed VHS / DVD) due to licensing issues, episodes of the show are very hard to come by. The only way that episodes can be found is through home recordings of the show from when it aired.
In simple terms, if they sold the dvds right now, they’d get sued by Metallica, Billy Joel, etc. for distribution of their music without a contract. It’s not worth the lawyer time to track down all the rights holders and make agreements if they only think they can sell 5,000 dvds.