When we have modern, proper software/APIs to work with to start. The addressable market size is already extremely small in comparison to everything else and the available tools are actually progressing really slowly. Performance matters too much in VR and nobody wants to try to take a huge gamble on a small market size with this junk. How do we still have almost zero multi-GPU support? Even Nvidia can't get most of their VRWorks features to work in VR Funhouse - a tech demo specifically designed to show off said features. Serious Sam VR is the only game I've seen that integrated LiquidVR and VR SLI... but despite doing what they could there they're limited by all of the layers and still reliant on closed drivers. AMD is getting better but Nvidia will never open up anything unless they don't care about it anymore.
Basically, no studios want to spend millions of dollars building their own modern game engine for VR when there is no guaranteed ROI, Cross-Platform SteamVR/Vulkan support is crawling, DX12 is a problem because half of the market refuses to upgrade to Windows 10. Nobody is talking about it but, as a developer, the current state of realistic tools/drivers/etc is a disaster... and then trying to support a game on top of that house of cards is even worse.
Finally, beyond a tiny, increasingly fragmented VR market... people want everything and they want it cheap. People complained when Raw Data had a $32 launch price and they still complain that it's $40. I hate to tell you... but that's as polished as we're getting for a game with any complexity. Serious Sam is the closest to getting there performance-wise but it's a much more simplistic game than Raw Data overall.
There are just a ton of self-entitled whiners in this VR market... and while 12-year-old kids don't hesitate dropping $60 on the next crappy EA Sports game for their Xbox grown adults are upset when a game that costs half that has a couple of bugs. Being a VR developer is thankless and miserable right now.
Let's just say I won't even bother dipping a toe back in until I can build everything cross-platform using Vulkan. The lack of commercial motivation when compared to DX12/MS (as part of the Windows 10 push) concerns me, though - we've seen this all before and with the Xbox/etc... plus companies like Nvidia that just make a disaster out of everything with their phony hardware-locked features and incomplete libraries... you'd have to be insane to attempt making a complete, original VR game right now.