http://3oamv2de6ooacy72hv3ulym3i3vvlprlkqas7hhzo4pu5nyxnji37zad.onion/blogs/writing-a-website-part-2
It is one of the very convenient ways to avoid eye strain. Well, it is not just the visitors, you might also prefer one theme over the other most of the time. While many debate about what is good for the eyes even now, switching between dark and light themes is an accessibility feature, and we are considerate to people with needs, right?