My understanding was that bands didn't want to pay for the rights to use the film footage after the initial license expired, which is usually soon after the single is released. Years later, when compiling video collections, the cost of using that footage again is something the band or record company can't be bothered shelling out for. It even happens the other way around, when movie companies don't want to pay the band for the song when putting together a comprehensive DVD, so we end up with a great DVD featuring interviews, commentaries, behind-the-scenes documentaries and deleted scenes...but no music video for that hit single, like "Ghostbusters" by Ray Parker, Jr. and "Cleanin' Up The Town" by The Bus Boys (both of which should have appeared on the Ghostbusters DVDs).
When Anchor Bay put out the Highlander DVDs years ago, they went all out and put the three related Queen videos and a bonus CD single into the set. Admittedly, the videos were not sourced from the masters, but from existing video collections, but it was a lot better than nothing.