I'm not sure why you think it HAS to be, completely, about the bottom line....
Because it was the subject of some hard negotiations with the union, and was only accomplished after the union voted it down once. Disney originally took the postion that eliminating the gratuity was non-negotiable (they were really hard-nosed about getting rid of it), but after that rejection, they sweetened the pot a little in other areas and it was approved.
But we've read enough "guest complaints" about service on the DDP, and not having control over the tip amount, to at least postulate that Disney may have been thinking about guest satisfaction in CONJUNCTION with their bottom line.
We do see those complaints occasionally, but I have two observations and one theory about those complaints. The observations are 1) complaints along those lines are immediately followed by numerous posts saying the posters have never noticed any decrease in service due to being on DDP, and 2) Our family's actual experience has been that we have never noticed any difference in service on DDP.
The theory I have is that many of the folks who advocate removal of the tip from DDP do so because they don't want to tip 18%. [NOTE: I am NOT saying that applies to anyone here, but I've seen it on other boards, primarily the DDP board.]
Not everyone normally tips 18%...or even 15%, for that matter. And there is a school of thought that says the DDP is a discount plan, and therefore the tip should be based on the
discounted price of the meal -- not the menu price. You can't just come out and say that -- because you'd get flamed for being cheap -- so some people say they want control over the tip when they
really mean they want to tip much less than 18%.
The truth is, we have control now. If a server doesn't deserve 18%, just go to the manager and complain and ask them to adjust the gratuity. I would certainly have no qualms about going to a manager if I felt I'd received substandard service.
And complaining to the manager is a much better way of addressing poor service than withholding part of the tip. If I withhold part of the tip, the manager doesn't know there was a problem and the server just thinks I'm cheap. If I talk to the manager, both of them know there was a problem and they can fix it.