Comment by gkoberger

Basically that the multiple departments involved have different objectives.

Imagineering is trying to build the coolest things possible, and many times the things seen in parks are play-tests.

Operations has to find the money and resources to keep things going, and these things take a lot of people to run.

Marketing sometimes will often provide the budget to make things happen (to promote a movie, etc) but it's not sustainable. They'll often sometimes use impractical inventions for marketing reasons, since they exist and might as well be used for something.

That's the main gist, although there's some interesting points about the risk to the brand (especially with camera phones) if Mickey ever slightly malfunctions in a public setting.