Because when VR/IRL movement are the same, there's no need to fool the body's systems.
The target audience for VR is everyone.
A lot of discomfort for relatively little (at least thus far) gain.
Aww. But I already had my scalpels out for DIY inner ear surgery. I just finished watching the YouTube howto and everything... :(
1) Don't move your POV in VR.
2) Train your brain interpret movement in VR as world movement not body movement. If you can maintain a sense that you're not actually moving just because your eyes are showing a lot of stuff moving around you, then your vestibular system and vision system will be in accordance and you won't have any motion sickness.
Children who use VR from a young age will have an easier time of this, but adults can learn it too.
People with really bad cases of motion sickness have problems playing games on a flat screen let alone in VR. I don't think we'll be able to do anything for them in the near future.