I was recently re-reading an Entertainment Weekly article about the "remaking of Star Wars" that came out prior to the 1977 Special Editions and a couple of people implied that there were two major reasons for the SE and neither had to do with George's "original vision." It was suggested that Lucas was testing the waters to see if there was still major interest in Star Wars. With the SW Trilogy SE's bringing in about $250 million domestically (that number would be a lot bigger now if you adjusted for inflation), it really wet people's appetites for the prequels. I think that had there not been a Special Edition release, Phantom Menace would have had the giant buildup that it did and probably would have made less money.

The other theory proposed in the article was that Lucas wanted his team to test out some of the cgi they were going to use in the prequel trilogy. Adding cgi Jabba into a 20 year old scene with Han Solo was a test-run of techniques Lucas would later use in the entire prequels. Hence, we had a zillion scenes were human actors were reacting to cgi characters added in later.

I think this makes a lot of sense. GL has since gotten so caught up in this "original vision" stuff that he can't go back and release restored versions of the OOT. That would contradict all the stuff he's said for the last 10+ years.