Movies especially with re-releases. Star Wars with Lucas tinkering and blocking old copies.
But we have this - https://www.thestarwarstrilogy.com/project-4k77/
"97% of project 4K77 is from a single, original 1977 35mm Technicolor release print, scanned at full 4K, cleaned at 4K, and rendered at 4K."
Opening scene comparison - https://www.youtube.com/watch?v=P1b47UP6ZGI
to my eye there is quite a difference .. in favor of the 4K77 remaster !
Doing God's work.
It was bound to happen with Star Wars, given how big a series it is. I wish we could have the same with more, but the amount of effort is huge in many cases, and literally impossible in others.