Dark mode is for people who prefer dark mode. Yes, the science seems to indicate that light mode is generally more readable, personal preference be damned.
I'm generally a light mode person, despite growing up on "dark mode" (AKA 8 and 16-bit home computers and DEC VT terminals). But, for whatever reason I have to code in a window that is set to dark mode.
Not all of us. I have a fairly strong dislike of dark mode/themes. However, I certainly wouldn't be upset if there was an option for one on HN, as long as I didn't have to use it.
I'm serious - try it. Only issue is that some monitors' dimmest setting is still too bright.
You could also get a user-styles extension.