It all depends on how you define remaster. In the music industry, remastering is done because older magnetic tape is not very stable, so it is a question of transferring to a new medium and (at the same time) getting as much information as you possibly can out of the original master. With the remastering of a film or a TV series, it can be done without substantially altering the original work, but someone in the chain of command often makes the myopic decision to "redo" the special effects and add in sound effects, arguing that current audiences are "too sophisticated" to accept the old version. Ironically, this results in a dumbing-down of the original in many cases. There are only two cases in which I found such tinkering to be justified: Star Trek: The Motion Picture, and Ghostbusters. In both cases, the tinkering was done to correct errors made at the time of release (unfinished special effects for both and with ST:TMP, a re-edit because the booking date for the film resulted in a rush job on the editing).