Speaking only for myself, there are two big reasons I never go to 3D shows anymore.
First is that the technology is just plain uncomfortable. The glasses feel bad, and my eyes hurt after a while.
Second is that filmmakers seem to have no clue how stereoscopic depth perception actually works. Objects only have perceptible parallax out to a couple dozen feet. Beyond that, depth is perceived purely by other means. But 3D movies keep applying parallax to objects much farther away. All this does is make them look closer and therefore smaller. The worst example I saw of this was an IMAX film at the Smithsonian about the development of the Boeing 777. There was a scene of a distant 777 in flight which popped the plane out of the screen. The result was that this 100-ton building-sized machine looked like a child's toy.
If the technology can be improved so it doesn't hurt, and if filmmakers can figure out how to use it without it looking utterly stupid, I'll give it another shot. Until then, I'm sticking with 2D.
The 3D movies I've seen were just too dark. Add to that fingerprints on ill-fitting glasses and the faintly cross-eyed feeling I get watching scenes where the 3D is pronounced, and I'll much rather watch a nice, bright, 2D version.
To each his own, I guess: the lower brightness is actually the main thing I like about 3D. It's occasionally done well enough to add something to the movie. Other than those cases, the only benefit is having not as bright a screen in a dark room.
Not that you asked me, but here's one reason: I have keratoconus and even with glasses and multiple eye surgeries don't see 20-20. Moreover, my right eye is considerably worse than my left, which means that I can't quite get binocular vision to work, making 3d viewing impossible for me. I realize folks like me are a tiny minority, however.
Perhaps a broader reason is that 3d seems to encourage filmmakers to go for visual spectacle over good storytelling.
3D gives me a headache. It also looks rubbish. I watched Gravity in 3D after Mark Kermode admitted it added something. It was bearable because it was a concise film and was enjoyable. But it works only in specific cases like these. It's more like a theme park ride than something that works on any film. Other times I was forced to watch 3D were: Dredd (only available in 3D), The Hobbit (was curious about 60fps which was only available in 3D). I regretted it each time.
For us it was Avatar, but at least both of us couldn't stand it. I couldn't focus due to the 3D glasses not sitting at the right distance in front of my real glasses, and my bespectacled girlfriend got sick about 20 minutes in. We left, got our money back, and never bothered with 3D again.
"Because I don't like gimmicky depth, distraction from the story, and worse dynamic range, and I'm not 5 years old to care for floating Ice Age characters...".
3D movies aren't real 3D, they leverage a subset of what we have learned to judge depth by independent of (and inconsistent with) other depth cues.
I can certainly see how too much early exposure would actually interfere with the development of the usual association of cues that support perception of distance.
