Disney also made Reedy Creek build and operate those garages, making the "municipality" float bonds to pay for them. It's part of the shadiness that was Reedy Creek. While I diagree with De Santis' motives on taking over Reedy Creek, there was a lot of that kind of shifting of responsibility for improvements from the company to the municipality when it suited them.
At this point they COULD build a garage just about anywhere, but it's still cheaper to build surface parking and tear out more trees.