I don't think we disagree... I'm not inferring that VR needs it to be immersive, just that it would add to the overall experience perhaps a bit more than it does to flat screen games. And just to qualify that, I'm also mainly thinking next gen where the resolution of the headsets would be more likely to be at a point where you would notice the smaller details like that more readily.
Basically my thought is that in a next gen VR headset, it's more likely to nag at you that the lighting/reflections/shadows are wrong than when just looking at a monitor as VR is by it's nature more immersive in the first place. All the small details being correct will just help build that level of reality, even on a subconscious level.
To that end, I do indeed hope that ray tracing does start to gain traction from this point... everything has to start somewhere. I, for one, however don't think it is currently worth the entry price - doesn't mean it still won't be worth it a few years from now.