I didn't have time to watch the video, but I assume this has something to do with rights for music used on the show.
We have the same problem with one of the most brilliant TV dramas of all time, the three-season (and tragically all too short) series American Dreams. They had all kinds of current (for the time) groups on impersonating bands (like the early Kinks) from the days of American bandstand. Season 1 was released on DVD but seasons 2 and 3 will probably never see the light of day.
P.S. I totally agree that WKRP was a unique and wonderful creation.