Hate to bring science into the EOF but there actually has been scientific research done into why people use white themes rather than dark. One reason being that
approximately 50% of the world population find it to be much harder to read white text on black than black text on white. Part of this has to do with light levels: with a bright display (white background) the iris closes a bit more, decreasing the effect of the "deformed" lens; with a dark display (black background) the iris opens to receive more light and the deformation of the lens creates a much fuzzier focus at the eye.
There is even research that states using a dark/black theme for long periods of time is dangerous and does really bad damage to your eyes.
