Accordingly that's because the company somehow managed to hide that all the way through developmemt and release.
But despite the fact it's not public knowledge, the families of anyone stuck in the game all determined the best course of action was to hospitalize. Without removing the headgear. The headgear they didn't know was dangerous. That's how they don't die after years of imprisonment.
I mean, the hospitalization is absent from the anime, but the alternative we're presented with makes less sense. Apparently comas make life sustainable for multiple years without food or water.
This show is stupid.