A large proportion of the population (5% or so, and by no means limited to one-eyed people) don't have stereopsis, the ability to fuse the slightly different images from two eyes to get a three-D image. For them, all these gimmicks are (even more) worthless.
BTW lacking stereopsis is *not* the same as having no depth perception. The brain interprets many "monocular cues" subconsciously to create a sense of depth (near objects look bigger than distant objects, if you move your head, near things shift more than distant things in your field of vision, etc.) Because of this, most people without stereopsis aren't aware of lacking anything and you need to do fairly complicated tests to pick up the lack. (It's also not an all-or-nothing thing, people may have different degrees of stereopsis.) Stereopsis is really just the icing on the cake of depth perception in real life. That may be part of the reason why attempts at 3D in movies and TV aren't all that impressive, come to think of it, though I'm just guessing there.
[I'm an ophthalmologist.]