You don’t expect Superman to be anyone other than Superman. You cannot imagine someone who can do all the things he does just going to a shitty job, buying groceries, waiting at the DMV.
Clark’s personality, mannerisms, and general nature are what set him apart from the living iconography of the Man of Steel. It’s ridiculous to ever even think of one as the other, regardless of how much they might look alike.
No one anywhere goes looking for Superman in an ill-fitting suit, behind a desk, drinking the office coffee because SOMEONE has to drink it. That is precisely where Clark Kent lives, in the paper margins you don’t think about, that guy on the elevator you see every morning, You think you said “hi” to him once when you were getting a hot dog.
I’d like to add that I think that scene with Lex Luthor literally spells out all anyone needs to know about Lex’s villainous personality perfectly
Lex Luthor CANNOT BELIEVE for even a second that Superman would be an “ordinary” person
Lex’s paranoia about Superman is sometimes treated by writers as actually being grounded in noble reasons and that really does totally miss the point of Lex’s fear of Superman…Lex is paranoid about Superman because Lex judges him by his own shitty standards
Lex is a crooked scumbag who has lied, cheated and stolen to get where he is and views basically everyone as being Secretly A Bastard because he himself is one. So when he sees Superman, a being with these fantastic powers who does good he immediately assumes he’s just as shitty deep down as he is because Lex Luthor cannot believe for a second that anyone can actually just be a decent human being
So even when literally ALL THE EVIDENCE points to Superman being Clark Kent Lex is just like “No one with the GODLIKE POWER OF SUPERMAN would ever setle for such a mundane and ordinary life!” because Lex can’t believe that maybe Superman is just an ordinary person who wants to help people and get on with his life