E-ink actually doesn't as it only uses power when pixels change between black and white and not when it's displaying a static image. E-ink uses the same amount of power rendering white text on black as black text on white. However, white text is more common since e-ink is specifically meant to imitate printed pages, and assuming it's not backlit, also doesn't have nearly as bad eye strain issues when in light mode as a glowing screen does.

It only has to update the parts where the words changed and it only uses the energy to initially change the screen. It literally uses more energy doing full screen wipes (flashing between black and white three or four times) to avoid ghost images. It would significantly reduce the need for a refresh if it was mostly black.

Our eyes are more sensitive to variations in lighter colors after all.