Yes, that is a strange omission. My first VR experience was using his equipment at a VR conference in the 90's, playing a virtual tennis game. It was cool as hell, but during a 'racket' swing, I accidentally smacked an observer that got too close. I still like to think it was one of the first "VR accidents."
Just a few years later, I bought one of these: http://www.mindflux.com.au/products/io-display/iglass3D.html
It was crude and required way too many cables, but playing Descent was awesome.