True, but the UCS SW sets came in 2000, a year after the first (and very basic) Star Wars sets were tentatively released by Lego and flew off the shelves. Had the line sold poorly we probably would not have seen them. Additionally, Star Wars had an estabished AFOL fan base given that many of us are (ahem) old enough to have seen the OT the first time round which justified the risk taken in developing the UCS sets in the first place. I don't think you can say the same for POTC.
However I would be delighted if Lego released plans for any UCS sets (of any genre) they might have designed but never released, perhaps in an ideas book or CDROM?