Like LAME uses a low pass filter unless you explicitly disable it, even on the "insane" preset it cuts off about 20khz.
But I can still understand why mp3 is still used, if only because of compatibility and intertia of keeping a collection in a consistent format. I see the worries about file size becoming less important over time, so many people I don't don't really see an advantage to a more modern codec like Opus.
And piracy has always been more about "branding" that people seem to like to admit - many video rips were labelled DivX for years after they had already moved to other mp4 encoders. And over the years the "brand power" of various pirate groups was surprisingly large.
And I suspect that mp3 and flac were the last "big" changes that made a significant difference to many end users, so newer formats just don't have quite the same improvement to promote their own branding.
Neither does the human ear.
While there may benefits for intermediate representations during mastering/modification, for playback higher frequencies can only ever make things worse as it increases the chance of unintentional frequencies causing distortion etc.
And for those intermediate steps any lossy compression is probably a bad idea.