hairy_hen said:
A lot of the blame for this rests squarely on Lucas himself. By creating the special edition in the way he did, he opened the door for others to follow. He's the one who first put the thought of changing films out there in the first place, and since ideas are pretty much impossible to eradicate, this way of thinking has spread to an alarming degree.
No one else modifies o-negs, though.