The hardware requirements are based on the 90 FPS requirement for good feeling VR. That extra 5ms of savings is quite difficult in a lot of experiences. And even without all the "good" looking graphics requires quite a serious amount of rendering hardware to get consistent, which is very important.
You're not going to get the standard AAA experience level graphics in VR, you're talking about a ~20ms difference in render time, with twice the amount of view to render (In polygon processing at least) But good VR is very sensitive to hardware performance.
This is not a requirement. It's a nice-to-have. 60fps is good enough for most people. 75fps is good enough for the vast majority of people. And asynchronous timewarp largely makes the issue moot, too.
Regardless, Microsoft bought Mojang for $2.5 billion dollars. Zynga has a market cap of $2.4 billion. I think the era of AAA games like Call of Duty being your main cash-cow are over.
You don't need to spend anywhere near all of your cycles to make a good VR experience.
You're not going to get the standard AAA experience level graphics in VR, you're talking about a ~20ms difference in render time, with twice the amount of view to render (In polygon processing at least) But good VR is very sensitive to hardware performance.