There isn't, except that it makes it possible to selectively enable them on certain sites. They don't bother me for things that I use regularly and already have them cached, like my bank. In fact, without them a lot of UI elements like carets and button icons become junk.
I go back and forth on allowing it to set background and text colors. Forcing black text on a white background does make some pages pretty ugly, but it does force everything to be readable.