Humans are extremely sensitive to the eye position being wrong, to the point that your VR headset has sub-millimeter adjustments for eye distance. Rendering both eyes from the same position only works on things very far away. Old versions of UE4 actually had support for monoscopic far field rendering for mobile, although that was removed for some reason.
I’d imagine the main reason Nanite and Lumen won’t work for VR is that they seem to do a lot of processing outside of the render passes. The brute force approach to duplicate all the resources and work for each eye might not be too difficult to hack in, but it would drag down performance so much that it would be completely unusable. Epic would probably not be very keen on supporting that as a feature.
If I remember right, they are planning on implementing Nanite but not Lumen for VR.