The risk/reward tradeoff of helmets is potentially dying, and we still had to make laws requiring people to wear them.
Glasses also have a pretty compelling reason to wear them.
I don't think VR has as compelling of a reason, at least so far. Even if it does, you need people to get far enough in to see that reason which is a hurdle when it involves a device they don't want to wear.
Until VR is done via glasses or some wire you stick in your neck matrix style, it will never take off