Lucas is of course the biggest offender, but I think that the fact is that digital makes it a lot easier to make alterations and it leads many directors to do it "because they can." I only recently discovered Cameron's hideous revisions to ALIENS and T1, Michael Mann's revisions to his Criterion releases, what Walter Hill did to THE WARRIORS, etc. And that's not even counting THX 1138, which is never getting fixed. I think that digital has made many filmmakers to engage in revisionism just because it's easier.