[bjornornorn]

I like to think of this somewhat differently.

By using extreme values you are limiting your options. If you use #FFFFFF in a design you can't select a brighter color and you can't select a color with the same brightness that's warmer or colder etc.

The same goes for black and for strongly saturated colors. You can't make something more saturated than #FF0000 and you can't create a brighter color without decreasing saturation.

Using these "extreme" colors can increase contrast and might help make details in a design pop, but that is only possible if you limit their usage overall. Do use black, white and saturated colors, but be aware of what you are sacrificing.