The final Mr Moto book follows two American spies in 1950s Japan and shows the nerve-wracking attention to detail they must have to keep their covers solid. Everything they say and every gesture has to fit the characters they're supposed to be, in case enemy agents are watching suspiciously.
The Silver Age Superman must have felt like this, surrounded by prying eyes waiting for him to give himself away. No wonder he needed the Fortress of Solitude.