I’m also a fan of Clark. While it may be considered an old trope, it’s still effective. As a Superman fan, believe me, I’ve had this conversation many times:
Most people don’t know or assume Superman would have a secret identity. They assume he’s Superman 24/7. We know he has one because, as the audience we’re privy to it. To the people in the streets in Metropolis, unless they’re connected to a superhero, they’re not aware of secret identities.
It also helps that Clark and Superman have been seen at the same place at the same time thanks to robots or shapeshifters. So even if people were to suspect, seeing the two together throws it off.
Considering we live in a world where everyone is trying to look like someone famous, adopting certain looks, if people saw Clark on the street and thought he looked like Superman, they’d probably just assume he was trying to look like him on purpose. Look at all the Kardashian wannabes out there.
Finally, I’ll always remember that issue of Superman where Lex uses the most advanced computer to deduce who Superman really is. The computer correctly names Clark Kent and Lex doesn’t believe it; he thinks if Superman had another identity, it would be someone of power, not a reporter and blames a “faulty” machine.
Like I said, I’ve had this conversation many a time lol