See: people calling any animated image a gif, even though many are apng or webp
See also: “Why does the Save icon look like that?” Most computer users these days have never in their life seen a floppy drive, but they still recognize it as the save icon.
I've seen my aging father change settings on a new computer to turn on showing file extensions on Windows, because he and a lot of older users were on the cutting edge of computing back when knowing the file extension was useful for choosing how to open it.
Sure, I'm acutely aware that there are stupid users out there; I've worked I.T. But there is also a whole spectrum of computer users with varying levels of computer proficiency out there, who us "computer people" don't see because they're not the ones who necessarily need help or cause problems. You can't necessarily extrapolate a visible minority of incompetent computer users to make statements about the entire population.
I don't necessarily have an opinion on whether that's enough justification to get rid of the .zip TLD. I'm just tired of the anti-user sentiment I'm hearing here.
Man, you're lucky. My aging father doesn't know how to change the inputs on his TV. And he doesn't understand why "our Internet is down" implies "the TV will not work" when the TV is clearly working, because it's telling him that it "can't connect."
While an OS may hide extensions, not everything does. Notably, gmail shows the file extension for attachments.