My general observation on this topic in a light-hearted way: The only toggleable option SV will probably ever do is full nudity.
So, something that many mainstream games will do (toggeable helmets), SV makes their game in such a way that many of its core players won't want it.
While something that many mainstream games won't do (full nudity), SV makes it so that a number of players will want it... for 'imaginative' reasons. I won't go into the things I've seen players do with it in-game.
You're looking at a game that is both violent and gory, and just one step away from also being a virtual online *ahem* game.
When players want to see each other's character faces, they want it to be as... 'uncovered' as possible. Only in this case, it isn't for the virtual online thing.