Actually, it really doesn't. You can prove me wrong by linking to any study where a VR rig has caused any physical change in the human body. Otherwise, you're just spewing FUD.
Not to say you can't harm yourself with conventional setups, you can (epilepsy being the extreme example, but eye damage from using displays irresponsibly is very common in the geek world), just VR adds whole new dimensions to it that should really be far more openly discussed.