No_color: Disabling Ansi Color Output by Default

This is a very questionable heuristic. I'm not sure the exact date that support began, but I have been piping color output to `less -r/-R` for decades. This can be nice even for less than multi-terminal-page output just for "search".

isatty(stderr) would actually be more accurate for my specific use cases for when I don't `|&` or maybe even `isatty(stdin)`, but those are also imperfect heuristics.

The point is, since "auto" is a questionable heuristic, it is not so crazy/wrong to just default to color-on and have an off switch and that off switch is what NO_COLOR is about (as explained by the very first sentence in the linked article). Desirable defaults ultimately depend upon the distribution of your user's tastes (as always, more|less).

NO_COLOR is orthogonal to the isatty suppression.

NO_COLOR ensures that colors are off even when stdout is not redirected.

For example, when you have poor vision, poor quality display, or sit near a window, (or worse – a combination of these) the colored parts of the output might have lower contrast, low enough to make them impossible to read.