Why stair at grass when you could stare at deserts, oceans, live animals or at the earth from the ISS?
If I wanted to watch TV, I could do that too. It's not really what I want.
Also, I think there's a big difference in focusing on something 5 cm away vs focusing on something that is a 100 m away. Part of the reason I spin around and put my feet up and stare out the window is because I want to stop looking at a screen.
When I'm stuck on a problem, I stare out the window or go sit outside with a pencil and pad of paper.
I can't imagine I'd be happy working in a VR setup. I could see it being useful when I want some type of virtual presence (at least until I start feeling sick), but I only need that a few times a year.