It's what you're sometimes given to wear under the goggles when you take part in a demonstration at a Virtual Reality show. It turns out that large swathes of the population wear face powder, and you don't want it sticking to the goggles for hygiene reasons. It sticks to the mask instead.
Of course, if you're one of those people who routinely wears face powder, you're not going to want to wear the goggles in the first place.
VR is still a technology of the future.