Guess what happened? DVD sites and fans kept asking him every day since DVD was invented:
Please release Star Wars on DVD.
But he said no, he wasn't done with them yet.
Then Phantom Menace came out, and by the end of that year we again were asking him: Please release Star Wars on DVD. Other movies get DVD's in the same year they are released.
But Lucas said: I'm not ready yet.
Finally he changed his mind and released TPM and told us AOTC and ROTS would follow a normal release strategy (which they did).
People were happier, but still we were missing the classic trilogy.
Finally when he did release the classic trilogy in 2004, he said the reason he changed his mind was because his advisers were telling him that due to rampant DVD piracy and newer formats on the horizon, there might not even be a DVD market by the time he's ready.
So he released the films as they were at the time while work continued on them for the upcoming rumored 2007 set.
Sure they aren't finished, but then neither were the original versions.
Most film makers just leave their films at "well that's how it turned out".
Lucas is one of the very few who put a ton of money into making these movies the best he could make them (in his opinion of course).