While I understand what you're saying I think the premise is a little off. It is not that Disney said: here is your discount tickets and then on occasion we are going to throw some extra stuff in too. Annual Passes are sold by Disney with a clear group of inclusions when you buy that include: park admission, parking (on some), a certain group of discounts and such. Disney over the past several years has decreased the things that they include in an annual pass. And in the case of many of us has changed the terms of agreement mid-year in our one year agreement. For some that diminishes it's value. Some AP holders buy into the whole package, not just the park admission. At the end of the day each of us determines if and what the value is in purchasing an AP.
One last thought. Yes AP holders do get a nice discount in terms of admission (though some would argue that an AP is an major expense), but when my AP expires and since I am not renewing, the chances of me buying a single or multi-day ticket is nil. So in the end Disney will not only not get my AP renewal money but will also not get any money that I spend in the parks or at other experiences on property.