I recall one pioneer from MIT bashed glass, pointing to his experience with having a single image in a different focus area/off-center as being uncomfortable for prolonged used (or maybe even harmful).
So that might be one reason (similar to how everyone realized in the 90s that VR made people throw up -- no market).
As for a smart-rod -- I really liked Canonical's push towards a viable use-as-phone-use-as-computer OS. It's an obvious idea that I think is already "proven" by stick-pcs and chromebooks. The cpu of a previous-generation smart-phone is enough for many tasks.
Another "proof" is what's happening with Samsung's Gear VR IMNHO, eg: http://vrjam.challengepost.com/updates/3462-meet-your-mobile...
Not sure if VR might not actually be an area where going wireless might break down though -- Oculus has spent a lot of effort getting the latency down. Still it seems it should be possible to do a lot of the 3d stuff along with head tracking in the head-set, and do more complicated physics modelling on a more powerful device.
Either way, I'm hopeful that we'll see more meaningful separation of devices as bluetooth (as I understand it) keeps getting support for lower power in one end, and higher bandwidth in the other.
But how come heads-up displays have never come to market in a serious way? I'm not counting Glass, by the way, given the focus on sharing rather than using.