The reason the Swan and Dolphin, non-Disney hotels have their prime location is the simplest reason of all. Money.
The details are at the time EPCOT was being completed and Disney wanted luxury hotels in the area, the company was flat on its back, on death's door broke. This was during the time the company was being rescued by the Bass Family (with backing from Roy E. and Lillian) from sale and certain break up. EPCOT had maxed out Disney's resources, and the studio part of the business was a complete failure. When you need expensive hotels and have no money, you go looking for partners.
The near miracle turn around of the company beginning in the late 1980's, driven by the renaissance in both animated and non-animated film (plus huge increases in theme park prices), caused oceans of cash to flow into Disney coffers. You've got to think at that time they looked back and said, "geez we never should have given away those spots for competitor (or at least non-Disney) hotels.
Is the 25 year term true? If so, those 25 years should be up pretty soon.