I imagine it's a lot to do with history, going back to black-on-white being the way that people were used to seeing text on paper. It's also more effort to dev

I imagine it's a lot to do with history, going back to black-on-white being the way that people were used to seeing text on paper. It's also more effort to develop a dark theme, in my experience. Most frameworks and project templates just start you off with a light theme.