I have to wonder if the average user of a light-on-dark color scheme simply has their monitor's brightness turned up too high.
I have my brightness turned down pretty low on every display I own, to the point that even a pure white screen can bearably be looked at. I prefer dark-on-light color schemes because I can turn my monitor's brightness down even lower with them, and I don't have to adjust my eyes or monitor when visiting web sites (most of which are dark-on-light). Why bother fighting the entire web with custom CSS to match your text editor when you can make the defaults comfortable to look at?
I have my brightness turned down pretty low on every display I own, to the point that even a pure white screen can bearably be looked at. I prefer dark-on-light color schemes because I can turn my monitor's brightness down even lower with them, and I don't have to adjust my eyes or monitor when visiting web sites (most of which are dark-on-light). Why bother fighting the entire web with custom CSS to match your text editor when you can make the defaults comfortable to look at?