**Warning Of Spoilers for various Superman stories including Smallville (2001-2011), Lois And Clark: The New Adventures Of Superman (1993-1997), Superman (1978), Superman: Secret Origin (2009-2010), All-Star Superman (2005-2008). Click here for Part 1 and here for Part 2.
There are many explanations that exist as to why Clark Kent is able to keep his dual-identity as Superman secret. In fact there are too many explanations to reference all of them in this article, at least without readers no doubt feeling it is too long. Luckily, this article is only about the two prime ideas behind why Clark Kent is not recognized to be Superman. Therefore, we only need to look at a select few examples for both sides.
Now, the first school of thought is that Lois Lane and the rest of the characters Superman meets are idiots. This school of thought was most prevalent during the Silver Age of comics. Three prime examples of this type of thinking are “The Girl Of Steel” from Superman #123 (1958), Lois and Clark: The New Adventures of Superman (1993-1997), and Smallville (2001-2011).
“The Girl Of Steel” story suggests Lois Lane is an idiot when she rejects the truth due to Clark proposing marriage, while believing Superman never would. While Lois and Clark: The New Adventures Of Superman falls into this category due to Dean Cain’s portrayal only relying on the glasses as a disguise. In fact, this gets joked about by the villain Tempus in the second season episode “Tempus Fugitive” (Mar. 26, 1995). Though, in fairness, one could say that it should also be obvious in comics where the art style does not differ between the depictions of Clark and Superman.
The last example, Smallville, is perhaps the greatest proponent of the other characters being idiots. Primarily due to how most of the episodes simply have Clark and his allies hiding his identity by simply lying.
However, despite the sheer number of examples that propose idiocy as the reason, I believe that Clark is somewhat skillful as a master of disguise. One reason for my belief is that in real life, people usually have at least one story about being mistaken for, or mistaking someone else for a similar person. Throw in the fact that the 1978 movie Superman has Christopher Reeve’s Clark Kent using a different voice, posture, mannerisms, and bulkier clothes, and you can possibly see my point. Heck, the well-regarded series All-Star Superman (2005-2008) and Superman: Secret Origin (2009-2010) take this approach to different degrees.
For those still in doubt, there is also the factor of shape-shifters pretending they are Clark Kent (Action Comics #692 1993), magical means (Superman Reborn (2017), and various other ways that he has kept his identity under wraps. There is even a story called “Superman, You’re Not Clark Kent—and I Can Prove It!” in Action Comics #457 (1976) that points out how effectively he has hidden his identity. In fact this last example suggests, via his co-workers and others not believing he is Clark Kent, that both idiocy and the various methods can work together.
So, in conclusion, while a certain amount of idiocy has to factor in for his duel-identity to work, one should always remember that he lives a fantastical existence in a wonder-filled universe.