Very true. This is more coming from print media where you can get closer to true colors. This might be one of those things that needs a tweak when translating between mediums. Much like optimal line length.
Sadly we're still in the past when it comes to displays to be used outdoors, but if you compare a Kindle in sunlight, the white background is probably an order of magnitude brighter than any normal computer or telephone screen.
"Don't use pure black for text" or "don't use a pure white background" are total myths among designers. You'll never have anything close to a pure color on current display technology.
It also doesn't occur on monitors. White and black on a screen is not pure, screens aren't that good.