Oh, I really disagree. Just think of how tempting it would be for someone who was planning to go on a long trip, or two trips in one season. Pay only the first 1-3 installments and then just stop, because you're not planning on using it anymore? Normally that family would be buying 10 day tickets at a cost of somewhere between $350 and 500 per, while the cost of an annual pass is only $520. If you only pay for 3 installments on the AP you can get away with murder at $130 each -- only pay one payment and you're stealing it for $43: less than one day's admission.
If you live in Florida you are much more likely to actually make time to visit and use the pass throughout the year, as opposed to only once or twice. It makes perfect sense to me that they are restricting it this way. I can see perhaps also granting to DVC members, but not beyond that.