Also there are some modifications out there to the old Dish 6000 which allow Dish programming to be recorded on DVHS or files. So the studios want to keep the good stuff "out of harms way" by not having it available on PPV on Dish.
I'm guessing that a MPEG4 HD-PPV might loosen up the strings a bit, or even a "Dish On Demand" model. Still I'm surprised that this has gone on for so long. I've had Dish HD since early 2003 and the HD-PPV situation is the same today as it was back then. A few poor HD movies shown over and over, with a few special events thrown in to break up the continuity. So when you want to watch a movie at Primetime, there's usually a ballgame on which you don't sub to.