People believe that dark background makes extensive reading from the screen easier for the eyes, and many advanced users accustomed themselves to it while working without GUI. So yes, light text on dark background is and always has been especially common among programmers.
and many advanced users accustomed themselves to it while working without GUI
Ah, the old HN anti-GUI bias again.
As for the eyestrain issue, I suspect people don't remember how bad CRT monitors were until near the end. Getting a consistent, bright white was difficult and very expensive. Horrible dot pitch meant bloom between very bright and dark colors. Color-related eyestrain just isn't the issue that it used to be.
