For the most part, Ferris wheels are an amusement park ride; Disney is a theme park. The Sun Wheel is in a section of DCA that implies a Boardwalk, and the typical rides one would find there.

I'm glad they don't. I hate ferris wheels. Disney also doens't have most of the amusement park type rides. They have a few rollar coasters, but not your typical ones you see everywhere else. Thats why it is unique!
A huge slow moving wheel could have continuous loading and large capacity (like the London Eye)