When I have some time to kill, I may try to find a thread from years ago in which we argued over the future of 3D. I seem to recall I was sceptical.
I am not surprised at this. Whatever 3D adds to the experience of TV viewing, it takes away by the requirement to have glasses ready for everyone who wants to watch. On that basis, it simply can't work in the realm of casual viewing, or having the TV on in the background while cooking, ironing, doing homework or whatever else goes on in a busy family home.
Restricting it to on demand is sensible, because planned viewing is the only way it works.