I leave a dim light on all night in our bedroom because I can't stand the pitch blackness in our area. We do have little street lights, like those carriage lights on a post, but they only provide mood, not enough light to ward off things that go bump in the night.
I'm also easily awaken by strange noises (noises that I don't hear all the time). So if my DH turns over, that won't wake me up, but if he gets up and starts walking around, that wakes me up.
Having a dim light on all night prevents me from waking him up every hour asking, "What was that?"