Why Superman Needs Clark Kent

Seems pretty simple.  Superman lives the life as a super-hero, while Clark Kent earns the keep working for the Daily Planet.  

But, why not just be Superman all the time?

Action Comics #305 (October, 1963) sheds a little light on that idea, under a cover by Curt Swan and George Klein!

Why Superman Needs A Secret Identity

Leo Dorfman, Curt Swan and George Klein provide the Superman story in this issue.  Other than the splash page, the story starts in the here and now, with Clark and Jimmy doing some work at the behest of Perry White, but getting in trouble, as Benny The Blaster tries a robbery, and Clark thinks there is no way to save Jimmy without revealing his identity.  So, Clark goes through a few imaginary scenarios in his head....such as if he had revealed his identity as Superboy (at his parents request, as Clark was bullied).  Ends up mobsters would likely have killed the Kents, and Superman would end up alone.  Second time, criminals find out Superman's identity (thanks to Jimmy) and expose him to Gold Kryptonite, ending Superman's career.  The third time, Superman gives up the pretense of being Clark....but still wants to help, so tries an alter ego as Mark Trent, but cannot get a job, so ends up a homeless vagrant. 

With a little more thinking, Clark finds a way to sabotage Benny's nitroglycerin, saving the day without revealing his identity!

The Girl Who Hated Supergirl

The second story of the issue by Leo Dorfman and Jim Mooney has Supergirl dealing with Karen Blair, who seems to hate the Maid of Steel.  Linda Danvers keeps having encounters with Karen Blair, who professes a hatred of Supergirl!  As Supergirl, returning to Midvale to celebrate the day she landed on Earth (May 18, 1959), she even tries to arrange for her to fly Karen, but nearly kills her in the process.  Karen explains her father had invented a way to communicate with aliens, and was, as an object flew between the communication rays, setting his lab on fire, killing him and injuring Karen's brother, confining him to a wheelchair.  Supergirl, using Superman's chronoscope in the Fortress of Solitude, shows Karen what really happen that day (that an alien bat had flown into the path of the rays, reflecting them back).  Supergirl then gives her the plans to her father's communication device, as well as getting doctors to help her brother reacquire his mobility!