I bet they could lower it, but I can think of two reasons they might not want to:
1. Lower brightness would make the lighting look uneven, which people will complain about and might cause returns of people with unreasonable expectations
2. If they're using PWM to control the LEDs, going too low might make 'strobing' apparent
p.s. perhaps an easier to implement solution is a white-on-black mode: if they did this at the display driver level would seem trivially easy to implement. It's how I use my iPhone and laptop in the dark comfortably (although on a laptop this is sub-optimal since it messes up the sub-pixel smoothing, which with eink is not a factor)
Last edited by stewacide; 12-25-2012 at 12:58 AM.