D. Martin
Super Freak
That's some serious justification, and a lot of thought went into that.
I tend to think that in 1977 Star Wars Lucas just didn't have much money and by Empire the budget was large enough to get Vader some nicer duds.
Oh, I know that's the truth with the first film. But now that the films are all done, we can look at the full thing as one work, and I'm sure that was something on the designer's mind.