It could be the case with the DVDs too, depending on what rights were negotiated. Many shows have DVD-release problems due to music clearance; either they have to replace the original licensed songs with substitutes (like in one of the early VHS releases of Trek's "The City on the Edge of Forever" where all the uses of "Goodnight, Sweetheart" were replaced), or the shows have to be severely edited or just not released at all. This is why WKRP in Cincinnati
isn't on DVD -- because the music clearance rights are a mess. Nobody at the time knew they'd need to negotiate for future home-video clearances.