The Doctor Who releases are an interesting case in point because though they are given a retail release they are restored by a small team of largely volunteers.

While many of the episodes are lost, all their soundtracks survive because of fans taping the sound from the television on audiotape.

Every lost episode has some record partly because of fans taking telesnaps which add to the materials still archived by the BBC and the search continues for lost tapes and film around the world.

If this sort of practice was expanded to other films and shows and broken down systematically sites like this one could do some of the work. I suspect a lot of people would be happy to do it for free if they knew that a large chunk of the money raised went back into search, archive and restoration projects but in the hands of business alone I suspect Darwinian principles would kick in and erase important cultural artifacts from recorded history.