He hasn't figured out that we would much rather see new films like Indiana Jones 4, rather than a dozen different versions of Star Wars.
It almost makes me wish Star Wars wasn't very successful, Empire Strikes Back was a complete failure, Lucas directed ROTJ himself (and made a really good movie that was also unsuccessful), and then made at least 6 other great movies and never got rich and famous. Then, we would have a bunch of good George Lucas movies to watch (and the OT in the original version), and not these prequels.