Other things like more accurate reflections and specular effects add more to VR where subtle head movements that don't produce the correct response our brain expects impact immersion even when we're not able to consciously identify why the rendering is not quite right.
The additional performance demands of VR mean it will be a while before we really see these benefits realized but I think when it all comes together it will really improve immersion.
There are some other potential benefits to basing VR rendering around ray tracing too that might take even longer to realize. For example you can directly compensate for the optics of the lenses when generating rays and avoid the whole post process warping step and foveated rendering is very easy to incorporate naturally.