@Anon4Lulz you are right, and when we try to do it, there's a chance it's very hard to see what color the screen is as you're adjusting it.
We have mainly skipped it because our window is "small" usually. Overall, there has to be a white patch + text on the screen somewhere to make a good "choice" about what color to use. (Maybe we could make it 90% darkmode or something like that.)