Yeah, that was particularly bad habit of SNL back then. They hit upon a mildly amusing joke and then just beat it to death by doing it over and over when it was barely a little funny the first time.
It's a wonder they didn't create a "making copies" movie with how they were back then.
It was a sketch on something called "The TV Show" according to wiki.
It says they worked on a pilot for The TV Show, which had spinal tap as one of the sketches.
I guess it still started as a sketch so you are right in your point that sometimes these things start as nothing more than that but it wasnt SNL. Although the cast have all been on SNL at some point.
Oh, I'm sorry, you are correct. It was The Folksmen from A Mighty Wind that started as an SNL sketch. Exactly the same people, so you can see why I was confused.