How much of that is not having a Disney park an hour's drive from the port? The cruises I've been on (admittedly all 3 or 4 nights) have a lot of people "splitting their vacation week" betwen DCL and Orlando. I think a lot of the general public still views DCL almost as an extension of the parks.
I think that is really the inverse.. people say 'how can I goto FL without visiting WDW?' - more than people picking Orlando because they feel the need for their cruise to include WDW.