Just a thought--It may or may not have something to do with the suppliers that they are using.
Nope, just one of many policy differences between the two lines. There are a LOT of differences in all the lines. The two closest in their operations and policies are Princess and Cunard. You can actually use you Captain's Circle # with Cunard and they don't even issue you a past passenger # of their own. The same number is saved in the same system and interchangale for both lines cruises. In every other way the lines differ greatly.