Finally, the main, undeniable reason that 3D gaming failed is simple: gamers just don't want it. We don't want it now, and we never did. Sony tried to make it happen, and they failed. The 3DS achieved some success because of its glasses-free 3D technology, but it's really been first-party Nintendo games like Ocarina of Time, Super Mario 3D Land and the new Luigi's Mansion game that are keeping the console afloat.
No matter how many times we were told that 3D is the next big thing, we were never fooled into thinking we actually needed it. Hopefully we all remember that when the next next big thing comes along.