The millions of unknowing CUA users don't know or use any keybindings - they just click, scroll and select with a mouse. Arguably, it is also what made CUA the worst option - there is just no selection pressure from users, no complains is something is not working properly. Vim keybindings are so well supported compared to the share of users because vim users care.
I would also agree, that vim keybindings shine for programming, less for prose where one would be all the time in insert mode anyway. Emacs, oh, readline keybindings are less supported in general, but can be found in the most unexpected places - text fields and editors in macOS, console terminals. Now, CUA - I would not even know which editor I should use it with - some amount is supported everywhere, but there is not a lot overlap between let's say windows and macOS, so I would put this idea into a box with a label "Had some clear influence on things we use, but is mostly dead".
shrug same story as with POSIX - something so minimal in features and inconsistent between implementations can only work as a lowest common denominator and is without any practical meaning. Call it a victim of own success, it won't change much in practice.
Also, POSIX is from some 30+ years ago now. It's been replaced with the Single Unix Specification and even now there are a dozen odd certified compliant OSes, and hundreds more that could be but haven't bothered. Several Linux distros have passed, meaning that Linux is UNIX now.
POSIX/the SUS is very useful. There are more OSes that can pass now than when the commercial stuff was at its peak.
And there are de facto standards that are more use. A mate of mine jokes that the stable Linux app API is Win32 because WINE on Linux is now more compatible across more versions than any 1 distro's own packages over decades, and more compatible on more platforms than Windows itself.
But saying that, Linux itself is an ABI now, and you can successfully run Linux binaries, without Linux itself being present, on Windows, on FreeBSD, on Solaris/Illumos and I suspect on other OSes as well.
So, you are free to mock POSIX and Linux compatibility, but in real life, it's true and it is valid and it works and people pay for this. It is real and it is useful.
Similarly, stick J Random Punter in front of a text editor on Windows, macOS, or any xNix with a GUI, and they will be able to edit some text, cut and paste, and save it.
Put them in front of Vim or Emacs, and they won't.
For me, I don't give an electronic sausage how much use they are for a skilled programmer. That 2-para definition there is the acid test. Any editor that fails it can GTFO and DIAF.
This, to Vim heads and Emacs gurus, is a weird and heretical thought.
Tough. I have nearly 40 years experience in this stuff, across more OSes than just about any other living human I know could even _name_, and I absolutely stand by it.
Why die, vim is thriving and in a much better shape than CUA(I wont repeat myself). And no, there is no standard for CUA, only very loose conventions which are largely inconsistent. On macos in editors and text entry fields I have a better luck with readline keybindings than with CUA and it says a lot about how much of a “standard” it is.
So, why again should emacs care about it? There is no heresy, vim and emacs gurus just do not care, this ship has sailed long time ago. Today across every editor I have used in past 20 years (vim, Idea, emacs, VSCode) and across 3 operating systems vim keybindings are the most consistent thing. CUA is laughable, not only does the overlap not allow to work with text effectively, it is also completely inconsistent, such as usage of cmd as modificator in macos. You may stomp with your feet about it, but people will not care more. If anything, these highly specialized editors in their niches will survive any mouse-driven fad (and let is be honest here, CUA-influenced editors are all mouse-driven). So, go emacs, go vim, you are doing everything right.
I would also agree, that vim keybindings shine for programming, less for prose where one would be all the time in insert mode anyway. Emacs, oh, readline keybindings are less supported in general, but can be found in the most unexpected places - text fields and editors in macOS, console terminals. Now, CUA - I would not even know which editor I should use it with - some amount is supported everywhere, but there is not a lot overlap between let's say windows and macOS, so I would put this idea into a box with a label "Had some clear influence on things we use, but is mostly dead".