Stwreoscopy is designed to work for a single viewer in a sweet spot. If that setup is correct, it works beautifully. VR headsets master that aspect perfectly. However, a cinema must accommodate many viewers and this means that most of them must content with a less than optimal setup. Actually, I find it a little bit curious that the human brain can cope with the resulting distorted perceived disparity as well as it does.

Someone would need to come up with a true light field display. This would make steroscopy work for the whole area in front of the display. Paul Debevecs team made a daring proposal a couple of years ago to build a light field display from an array of Pico projectors, each one acting as a single pixel of the display. The viewer would need to look directly into the projectors. It seems that this project never got off the ground, though.