If you're looking for a company that will always agree to take a loss whenever you change your plans, I think you're going to be out of luck. Unless I'm completely misunderstanding, that seems to be what you want.

Your rate is based on the dates and times you provide when making the reservation. If you don't adhere to those dates and return the car early, you shouldn't expect any company to always offer a prorated refund. (That's especially true for a prepaid rental.) In a leisure market like Orlando where most people rent for multiple days, I'd guess that Budget will not be able to turn around and rent that car for just a day. So, your early return probably is causing them to lose money here.