Why don't people recognize Clark Kent as Superman?

I mean, it's the same person, the same face with slightly different hair style. People should be able to recognize him.Why don't people recognize Clark Kent as Superman?There is more than just the hair. His entire personality and demeanor are changed. He's timid and withdrawn, hunched, wears glasses. He basically acts like a geek-slash-farm-boy when not in costume. In which case he acts super-heroic, out going, and generally awesome and perfect. (In private he's a mix between the two. Lois and maybe Bruce and Diana are the only ones who really ever see this)Why don't people recognize Clark Kent as Superman?OMG Clark Kent is superman?