The pro-privacy, power user bubble, obviously. The one company that supports VR on Linux you're mentioning is Valve, which lets you use their headsets in any OS with no fuss. They fully support Linux, so I don't really know what you're talking about there. The Occulus line on the other hand, requires a Facebook account and tracks your data constantly. Obviously the overlap of Linux gamers and people fine with the Occulus ToS are pretty small. Conversely, the overlap of Windows users and privacy-conscious people who are knowledgeable enough to modify their OS is also very small.