I think that the biggest reason for the changes is to attract collectors. Collectors collect all variations of an item to get a "complete set". He has to make the new changes significant enough to make people want them for the changes.
I don't think that he cares, or even knows, about the problems with image quality. I think that it is apparent what kind of culture there is at Lucasfilm. George is the dictator, with a legion of yes-men at his disposal. The workers are concerned with the tasks and deadlines that they have been handed to them. Lucas noticed a few things that he wants fixed, but nobody is brave enough to tell him about the other faults.