Some things work as they are
We've always had sculpture and we've always had paintings. Theatre is usually less successful in the round than it is behind a proscenium arch. Avatar worked, on the whole, because its 3D was at the service of the story, rather than (in old 3D films) actions being taken (objects thrown at the camera) for the sake of the technology. So it might be that 3D TV, as a default, never takes over, as people won't wear special glasses every time they sit to watch, and because 3D enhances only the visual part of a story -- it doesn't help a weak plot, second-rate acting or poor direction -- and why go to any trouble at all if it doesn't bring benefit? I could imagine putting on the special specs for a special show, in the same spirit that I put on Brahms with my surround-sound but listen to my radio on a cheap little set int he kitchen.