>>313165578
The main problem is that for the world scale to match reality, the cameras have to have the same spacing as your own eyes, otherwise everything will be too large or small. Many completely fuck this up with the cameras so far apart that everyone is a giant. The other problem is there are only three degrees of freedom, so if you move your head in any way that isn't a rotation around its existing position, then entire world moves with you, immediately breaking any sense of immersion completely. They're arguably worse than just watching a large video screen with the headset on.