Edit: And a lot of modern black metal for example doesn't even bother with stating who they are. Member lists are pseudonymous or anonymous. I think this "anti god" culture makes metal different from other genres in some ways.
There's also upcoming math rock band Angine de Poitrine who are also anonymous https://www.youtube.com/watch?v=0Ssi-9wS1so . In these cases you can argue that the person doesn't matter but in my opinion it still does. There's a person inside that costume, who has made the decision to be anonymous as part of the whole experience. That's part of their expression.
Of course there's then bands like Ghost who have mainstreamed this too - the players wearing the costumes are usually just contract musicians and don't have anything to do with Tobias or the music other than playing for money. Good for them but f that, you are just a robot at that point.