Reading through the Silver Age Superboy, I noticed how many stories ended with this:
This is somewhat akin to the "Ending with Iris" bit in the Flash, and the "Bah!" responses from the Joker; a way of letting us know the story is over.
Update: Kirk House points out in the comments that the practice of ending the story with a wink from Clark may have originated with the Superman cartoons of the early 1940s from the Fleischer studios. Here's the first one in that series, which does indeed end that way: