An article from Business Insider details a few reasons why film studios and theaters are offering 3D, and why the medium will endure. The first two reasons, that theaters are installing more 3D projectors and studios are releasing more 3D films, don't really say much about what the public wants. Taken in isolation, these might just be gimmicks to lure audiences away from home video; or it could be bad market research; or doubling down on an ill-advised upgrade policy; or at worst a collusion between film producers and exhibitors to raise prices. (The argument that 3D is doing well overseas would support studios making 3D movies, but not domestic theaters showing them.)
The third reason claims that 3D movies are bringing in money. In my college business ethics class, my professor was adamant that the sole purpose of a business was to provide a service to its customers. I don't agree with that from an ethical point of view or in practice, but I do believe that free market pressures can enforce his idea nonetheless: give us what we want, and we will pay you; treat us like dirt, and we won't. I.e., follow the money. No matter how much studios and theaters want to make 3D happen to increase their own profits, if we reject the medium and stop buying tickets, they will back off.
So how much do we want 3D? The Business Insider article isn't able to separate 3D sales from sales that would have happened even without the 3D. The numbers for The Avengers, widely available in both formats, suggests that when given a choice, audiences are split down the middle, with half of us preferring 3D. The Avengers is such an outlier, though, we might have flocked to the theaters even if the entire film had just been the schwarma scene. Also, 3D ticket sales for any given movie measures how much we thought we wanted to see it in 3D; only exit polls of consumer satisfaction would tell us if it was actually worth it.
This Fandango poll (I don't know the sample size) seems reasonable, that half of movie viewers don't like 3D, another quarter might splurge for the right film (e.g., CGI/effects-rich movies), and the other quarter either prefer it, or want to prefer it if only the quality were good enough. I surmise that the poll would skew toward a youngish, internet-comfortable audience, slightly inflating numbers in favor of a technological innovation. (My parents, who both wear glasses while watching movies, were not excited at the prospect of layering on an additional pair of glasses for Gravity.) On the other hand, frequent movie goers (which I assume Fandango users are) should mind a price hike more than the infrequent movie goer, so if 15% are buying 3D tickets anyway, maybe America at large doesn't mind the price inflation so much.
For my own preference, I ask whether the addition of 3D merits an increase in ticket price and the slight discomfort of wearing glasses. Although I will often go out of my way to see a matinee showing for the reduced price, in general I don't think about how much individual tickets cost; I see as many movies as I want to and am able to, and just accept that the aggregate ticket price is the cost of having a fun hobby. So I'm not opposed to steeper prices if the product is superior.
I believe I've seen the full gamut of 3D movies, from the red-and-blue Jaws 3D as a kid, to the made-for-3D Avatar, to the mass of post-processing imitators. But the true test is to see both versions of a film, and I have now done this for three separate movies: Avatar, The Avengers, and Turbo. So here's an exit poll of one consumer: not once did the 3D add any extra enjoyment for me. I disliked wearing the glasses, but other than that, I simply didn't care. Why pay extra for that?