That is not the only reason that's been offered. A common one mentioned on this thread is that there are certain stories that are more difficult to tell if the character is a full-time, known superhero. Relationships with other people are, of necessity, different for a character if they can't blend in with others.
There's certainly room for characters of all kinds, and I don't suggest that every character needs a secret ID. But neither does every character need to be wide open. IMO, outing Superman is a mistake that will, eventually, be reversed. It's an ego move by an author screaming "look what I did" rather than stewarding a character.
Last edited by DrNewGod; 02-14-2020 at 08:52 AM.
Reading List (Super behind but reading them nonetheless):
DC: Currently figuring that out
Marvel: Read above
Image: Killadelphia, Nightmare Blog
Other: The Antagonist, Something is Killing the Children, Avatar: TLAB
Manga: My Hero Academia, MHA: Vigilanties, Soul Eater: the Perfect Edition, Berserk, Hunter X Hunter, Witch Hat Atelier, Kaiju No. 8