I'd go a step further and say that sort of loop is probably the first thing most people who play around with agent harnesses try, pretty much the first "Hmm, what should I do now?" thing that pops into people's head.
It's less the idea and more the simplicity of it. It's a distillation of something that works and lets newer practitioners get their feet wet before moving on to more complex implementation.
I believe Karpathy himself called it autoresearch, not Karpathy Loop, but in a vacuum of names around AI it seems to be very easy to meme-drop a name and then come influencer efforts to cool-name and normalize it. See vibecoding*