It's not even a given that Jabba has her in that outfit because he finds it attractive. It could just as well be to titillate human guests or a pure power play.
>>accoun+(OP)
Fair, although I think in Doylist terms it isn't that deep, especially when we're considering George Lucas. It's a common enough villain trope.
But Jabba did give her a good lick, so it seems like there's something he liked.