Or perhaps netizens who know every copypasta out there are actually a much more niche subset of humanity than we care to think.
I'm irritated at how dismissive this seems, so that's coloring this response, so mind that.
It's not exactly "every copypasta out there", it's been consistently one of the most popular copypastas since... 2014?
That just makes the point
even stronger. Ask joe blow types about the
most popular copypastas and they won't even know those. If you just grab someone at random and ask if they've heard of the "navy seals copypasta" be prepared for a
lot of blank stares. Almost all regular people only stick to instagram, twitter, facebook, they don't venture onto forums or places that they would encounter forum or gaming-related memes of that type.
One of the things that happened to me at college was a discussion of all those alt-identities like pico-gender, demi-sexual etc. I mentioned that a lot of that stuff originated with the tumblr community, and everyone in the class started yelling at me, "no it didn't! I've been on tumblr and never seen any of that!" ... but then the one guy who had started the discussion said "yeah, a lot of it did originate with a subculture of the tumblr community". So, in other words, 30 non-nerds, all of whom were on Tumblr due to them being content creators, yet hardly anyone had even heard of the fairly well known connection between Tumblr and the sjw / non-binary genders thing. Which is kind of a major deal.
Most people are willfully ignorant (and this is at
college) and if you tell them things outside their experience, they get actively hostile rather than interested to hear more. It's the Dunning-Kruger effect in motion: those who know the least about something assume that they know it all. They use
their knowledge of a subject to estimate how much there is to know. e.g. if they know nothing about something, they assume it must be a pretty small domain (which is patently wrong: any area you haven't ever looked into is probably a never-ending rabbit-hole of content).
Basically, average people live in a walled garden inside a walled garden and don't have the first clue about diversity or range of online life, not even the slightest idea. They think that 90% of the internet is on Facebook and that anything outside that must be a
small niche of content.