While they are built for different purposes, they are still 40+ year old editors that are still in use today. Although vi, or should I say vim, is still seeing more active development than wordperfect for dos, it's still true to its original ui and design. So, if you don't find weird that many of us are using vi on a daily basis, maybe we shouldn't find it weird that wordperfect for dos is still in use today.

Because it highlights the same thing: failure of modern graphical UIs.

The programmers that prefer VIM (or Emacs) to more modern fully features graphical IDEs are basically the same as the writer who prefers an old DOS program.

It means that old software was more usable and reliable to the point that a lot of people is more productive with it than modern programs. It is a big fail of the modern way of realizing applications.

The triumph of modern GUIs lies with the discoverability that the mouse/trackpad/touchscreen bring to the table. This is absolutely critical for onboarding beginners. In the modern day, computers are so ubiquitous that the vast majority of users are either beginners or dabblers (basically an eternal beginner).

Text-based interfaces have always been way faster at what they do (anything non-graphical). You simply cannot beat the efficiency of a power user who knows all of the keyboard shortcuts for their favourite text editor. I don't think that's an indictment of the GUI, however. The GUI ushered in ubiquitous computing akin to the personal automobile. Text-based interfaces remain a powerful, highly specialized tool for those who have the time and the need to learn them.

Yes in the general case, but not for text editing software. Discoverability is great in modern GUIs, for example a photos app on a mobile device. There are lots of options and they’re all mostly independent and needed in different cases. So it’s great you can just get started, click around at icons that look familiar and get results.

I would argue that this doesn’t apply specifically to text editors. 95% of all text documents are paragraphs with headings and inline formatting. With styles and display codes, WordPerfect lived up to its name. You could get the document looking perfect, exactly the way you wanted it. WYSIWYG editors look nice and could get you started quickly, but anything more than a letter turned into a mishmash of styles and fonts and spacing. The now-infamous ribbon in Word lets you discover and apply all sorts of formatting, but what you really want are consistent paragraph styles. Word perfect guided you into using those styles because the UI was restricted in just the right way.

Emacs' built in help is pretty good, I think. If you teach someone C-h f for function help, C-h k for keybind help, etc. I think they can get pretty far. The which-key package is great for discoverability as well. You can start pressings keys and then see a map of which next key presses do which action. I used vim for years, but always used a search engine to figure stuff out. I think Emacs got it right here. There's also the graphical menu system in Emacs, but I've always hidden it and avoided it.

what frequent action can't you do with ST3/VSCode's command palette?

I've been using ST for 8-ish years and never use the mouse/trackpad/touchscreen/joystick/stylus/trackball/wheel.

Or you know different people like different things and there are 7 billion people in the world to maintain and upkeep all of them.