Delux Dining not offered with Land/Sea packages - does anyone know why?

[hookedonears]

I called yesterday to enquire about upgrading our land/sea package on the Wonder in April, to add the delux dining plan. Disney Cruiseline said they don't offer the delux dining plan with their land/sea packages, only the regular dining plan. I guess I really don't understand the reasoning behind that. I considered looking into it once we check in at our hotel. Could anyone give us any advice with this issue.