Outside of IMAX cinemas, it seems ticket sales for 3D movies are lackluster as well (compared to 2D showings of the same film at the same location). Not sure if it's the actual format or just the 3D surcharge.

I imagine smaller chains opening new locations may pass on adding 3D capability to their theatres in future, however many may continue showing 3D films on the equipped screens if only to justify the extra $15k/cinema in equipment they were hustled into buying while making their mandatory 3D conversion.