Because “f*ing around with copyrighted material” is not a crime. We own the movies, we can do with them what we please, so long as it is for personal use. It is, however, a crime to sell duplicates of that copyrighted material, altered or not.
It’s a crime to distribute duplicates of copyrighted material, even for free. As you say, no problem as long as the work on the movies is for personal use, but there are legal issues as soon as it is distributed to third party people -whatever the way it is distributed. So in theory the fans who are distributing any original/restored/whatever version could be in trouble too.