1. The fans would like the original versions better. Oh, the horror!
2. The OOT would expose a ton of flaws of the PT and upset the kids who grew up with the prequels.
3. Millions of people would demand their money back for the 2004 DVD's
4. Milions of people would discover that the OOT didn't need any tinkering and all the changes he made, only made things worse.
5. People will discover that Lucas had no original vision.
6. Hearing Vader say "bring my shuttle" will scare children and send them into fits of rage.
7. Young fans will prefer the puppets, actors in costumes, man made sets and realistic look of the OT and demand Lucas do a non cgi PT.
8. Fans will be angry that 23-29 year old films don't look like they were made in 2006.
Seriously, what terrible act could come of a proper OOT release?