>>2431433In the first Star Wars, Lucas had this idea that there weren't bras in the Star Wars universe. Part of Princess Leia's costume was a wrap to hold Carrie Fisher's boobs in place instead of an actual bra.
It's entirely possible that Lucas stuck to that idea when he returned to the prequels, at least partially, so Padme's combat outfit there may have breast support, but otherwise Natalie Portman isn't wearing a bra (pure speculation).
Was that the explanation you were looking for?
