More people do it than you might think! I sit in an office of 8, there’s always someone either quietly beatboxing to themselves, doing minute long "uhhhrrmm"s or muttering movie quotes. There’s an understanding that anyone who feels bothered by the stimming can put on their noise cancelling headphones lol
Even porn? I’ve had a discussion at work recently about how crazy it is that media conservation often overlooks porn as something of “no value”, so it becomes lost media almost instantly, especially now in the age of streaming.
But I bet that future anthropologists would be really interested in studying it!