I am a long-time user of Windows High-Contrast Black color scheme and use the SP's high contrast mode. I have issues with my eyesight that make it very difficult for me to use the standard "bright" color schemes (it's like trying to find a polar bear in a blizzard for me). I have found MANY issues with applications in these non-standard color schemes and have come to the conclusion that most developers pay very little attention to usability issues of this sort. Simply put the target audience is too small to worry about. If it works, great, but if it doesn't they don't have the time / resources available to deal with it.
On a positive note though for those of us with vision challenges things have improved substantially over the years, but things still have a long way to go.