xterm is a de facto standard, in that you can sit down in front of a machine which appears to be running some flavour of Unix, it doesn't matter if it's Gnome, KDE, TWM, CDE, etc., GNU or BSD or Solaris or whatever, you'll probably be able to find xterm and work out the rest from there.
Many devs/hackers use xterm as their day-to-day terminal, and seem to approximate ANSI control code compliance with "works in xterm".
The problem with this situation, as mentioned on the st page, is that xterm is unmaintained and unmaintainable.
st is trying to be a maintainable replacement, making improvements like vector fonts, and not being shy about ignoring legacy/niche/solved-elsewhere features.
- I dispute "many devs/hackers use xterm". I switched away from xterm over 20 years ago, when it was clear that they were never going to have good support for anti-aliased fonts. I work heavily in the linux and with linux devs, and I can't remember the last time I saw someone using an xterm on a modern system.
- xterm is for exactly the case you describe: when all you have is "base X11" and you need a terminal. No crazy multi-gigabyte toolkit requirements. Its essentially a fallback/recovery tool for these cases, although I prefer just working on console when things get that bad.
- xterm's codebase is 30+ years old. "unmaintainable" seems like an overstatement, by a longshot.
xterm is a de facto standard, in that you can sit down in front of a machine which appears to be running some flavour of Unix, it doesn't matter if it's Gnome, KDE, TWM, CDE, etc., GNU or BSD or Solaris or whatever, you'll probably be able to find xterm and work out the rest from there.
Many devs/hackers use xterm as their day-to-day terminal, and seem to approximate ANSI control code compliance with "works in xterm".
The problem with this situation, as mentioned on the st page, is that xterm is unmaintained and unmaintainable.
st is trying to be a maintainable replacement, making improvements like vector fonts, and not being shy about ignoring legacy/niche/solved-elsewhere features.