Alter Ego

Superman was the first of many superheroes. And every superhero has a weird, dramatic, or traumatic backstory. It is not explicitly stated in The Superman Chronicles Volume One, but Superman was adopted by a sweet, stereotypical American couple living on a farm after he crash-landed from his home planet, Krypton. His parents named him Clark Kent, not Superman, and the dichotomy between his identities is evident. 

In science, more specifically in the field of psychology, there has been a long debate on what makes a person who they are - nature (genetics) versus nurture (environment). One side is not better or more influential but most would agree that it takes a combination of genetics and the environment to create the person that they are. 

Superman owes his powers of flying, super strength, speed, and basically the capability of invincibility to his genetics as a Kryptonian. However, Superman grew up as Clark Kent from the time he was an infant. He was raised as a human with American morals, values, and culture. He probably found it difficult to form his identity, who he really was, as he discovered that he had abilities that no one around him had. 

"But I still like you."

"Perhaps we'll meet again!" 

 With his instilled sense of liberal justice, morality, and righteousness, Clark Kent decided to become Superman. He could have become Superman full time, giving up the name and career of Clark Kent, but he didn't. I find it interesting that throughout the comics Lois Lane pursues Superman, but he brushes her off and tries to get her to notice Clark Kent. I think that he appreciates both identities because he can live a normal, human life as Clark Kent, and he can use his unique abilities publicly to achieve justice that most humans cannot as Superman.