Actors want to be able to emote, and studios want to get the famous faces they've paid for on screen. Think back to pretty much every superhero movie you've seen, specifically the big emotional and/or climactic moments. Remember how many of those include some kind of contrivance so that the otherwise masked hero or villain doesn't wear his mask, or it's broken, or ripped off, or whatever? Downey Jr in Iron Man and Avengers, Dafoe, Grace and Maguire in Spider-Man, Keaton and Pfeiffer in Batman Returns, Smith in Suicide Squad, Holland and Keaton in Spider-Man Homecoming, Stan in Captain America The Winter Soldier, Boseman in Black Panther, and so on.