From what I can tell, this is due to designers cargo culting low contrast UIs. Whenever I've asked designers for citations that grey-on-gray UIs are better than

From what I can tell, this is due to designers cargo culting low contrast UIs. Whenever I've asked designers for citations that grey-on-gray UIs are better than black/white or white/black, I haven't gotten any good responses beyond some subjective answers. It's considered "general knowledge" but I haven't found hard data supporting it. There are good reasons to avoid bright white backgrounds in certain cases since it can be hard to read in dark environments as your eyes switch between the bright screen and dark world. But in this case, pure white on pure black is still the best option for contrast. And the correct solution is to dim the backlight of the display to reduce brightness.