Almost nobody is testing their website with a screen reader so they don't think of it as part of the user experience. In fact, I think most developers are only vaguely aware of what web accessibility actually is for and how it affects users.

Ironically the site does not support `:prefers-color-scheme`.

prefers-color-scheme has shipped for something like 7 years now and not even all of the major sites I frequent which already have a dark theme toggle support it yet. Obviously accessibility is more important than a dark theme (though it can be part of an accessibility story), but if it takes a minute to ship prefers-color-scheme on those existing themed sites and it's been so many years you get the idea of how little it's about when something is easy or not.

Because 0.5% of the world population is blind and it costs much more than an extra 0.5% to make a website accessible?

Everytime this question is asked I wonder if people are genuinely not understanding that. It's just not financially worth it.

I'm not defending this position, but it's just glaringly obvious.