Star Wars is notable for how poorly the original elements of the film have fared. For one, the film negative had severe problems with fading which made it difficult to restore even in 1997, and it has only faded more since then. There is also the fragility of the negative - certain parts were lost when subjected to the cleaning process.
Most restorations, when faced with these difficulties, would turn to an interpositive print or (ideally) the color separation masters, but in the case of Star Wars the separation masters were botched in production or storage and the interpositives were badly degraded due to the many print runs struck from them.
Most old black and white or Technicolor films don’t have the problems of Star Wars due to being very dye stable over time, and after Star Wars Kodak fixed their dye stability issues. So Star Wars suffers from a number of issues and extenuating circumstances which are fairly unique to this film.