why would they want to sell more? APs can cost Disney potential $$ for example me and my wife spend over 21 days in park this year with our AP and we in Ohio thats 42 days of admissions. At even rock bottom Disney priceing if we were some how to have bought them in the the 10 day bunches at about 55 dollars per day, Disney would have made over 2300 form us. Instead of that Disney only made about 1600 from us. so that is a 700 dollar loss before you even counted the money they lost from Photopass, parking, room discounts, and food and merch discounts.
APs are a great perk and allow alot of us to go multiple times per year. But in saying this as a non syncical person. If Disney was to open up the AP to guests outside of florida, they would have increased costs for managing this, as well as it would make it easier for people to game the system. Say for example i bought at AP and was going for 14 days by myself. I could easily get a AP pay only 1/12 of the cost which would make it about the cost of a 1 day pass, as well as get discounts on food, room and other things. I could then Disapear before my next monthly payment, and Disney would have the problem of tracking me down and billing me or whatever. Yes Disney could cancel my AP but I already went on my vacation paid less then a 1 day ticket as well as was able to get discounts on food and lodgeing.. So I could abuse the system to easily and it could cost disney money on the bottom line.
At least by making it a bill that Out of Staters have to pay up front, makes it so Disney only looses potential revenue to the Discounts they already have in place.
Disney can get away with this at least in So Cal and Florida because these people would tend to be day guests and would be less likely to fully use some of the other discounts.
Now in saying that I love my AP and would even think about getting the Platinum Passport if I was going to have a DL trip in the same year as my WDW trips but I can see why Disney doesnt allow all passes to eveyone being something you can put out over 12 payments