For me it's a matter of contrast and a preference for low but balanced lighting. My wife can watch tv in a room with no other lights on but I can't. Same with trying to type on a laptop keyboard while looking at a bright screen. I usually don't have the screen on it's brightest setting anyway, so with my laptop "nightlight" I get something easy on the eyes both on and off screen.

The light is just to light up the keys--I can see the screen from across the room. The keys, however, are dark gray with light gray letters and they're nearly invisible in a darkened room.

Gary

I only worry about the up/down arrows, touch pad curser, enter key on stage...light is not a factor, the screen is suficient for me, but sight is very subjective. I also hate playing in briht lights , I always dim the room lights somehow on a gig also for atmosphere...
Guess I'm a hopeless romantic..