There are some reasons for that:
1. Hardware: Although advances have been made, HMDs are still too big and uncomfortable to wear for some people. There are problems regarding headaches and some people report feeling motion sickness after not too long. The screen resolution also needs improvement, as does the battery life.
2. Software: Right now, games are the mainly atractive software in this space. It still lacks a more robust software offering, easier to use. There is nothing you can do on VR/AR right now that you can't do on your phone or computer. 
3. Price: the cheapest offerings start from 399 US dollars, which is by no means cheap for a bulky technology with no clear use case yet that can't be achieved with more mainstream technology people are used to.

That might change sooner rather than later with cheaper and smaller hardware coming out to help on one front, while Artificial Intelligence might boost the software and lack of use cases side of the problem.
spam fails_task lang_mismatch pii not_appropriate hate_speech sexual_content quality toxicity humor helpfulness creativity violence