I think that the reason some hotels charge a lower price for these rooms is because for most people there is either a stigma with staying in one of them, or as mentioned before, the traveler just wants to save the room type for someone that truly needs it. By offering them at a lower price the hotel is trying to entice the general public to book them, like it or not.
If you book one, but don't truly need it, the best thing to do is to jot down a note in the "comments" field when you make your reservation to let the hotel know that you don't need the accessible room.