I think we agree then, the OP statements:
The trouble with trailers for 3D films..... ........is that they need to be attached to a 3D movie.
Is not necessarily true.
I disagree, what's the point of going to all the bother of doing it with 3D in mind if you aren't going to promote it appropriately especially as most of those going to see it will see it in 3D?
To deny/disgree with this is just lunacy. Is it a full moon tonight?