As mentioned Dish got into a lot of trouble selling out of market locals to subscribers and nearly lost the right to provide any locals at all... So, if DIRECTV or Dish find a sub in the wrong DMA they have to change them back. You can hide your address and work the system to get it, but if brought to their attention they have to respond.
I'm glad you mentioned that, most people think it's not a big deal and to a customer it may not be, but I'm sure it would turn into a big deal if the ability to provide locals was pulled.