I will probably jinx myself by saying this, but I haven't found myself having to change an alternator, or other major component on the side of the road or in a parking lot before. At home, I have plenty of lighting options.
Besides, regardless of where your light is coming from, your hands, tools and/or head is in the way and blocking much of the light for where you are trying to see anyways.
Fortunately, I do not live where much of a chance of going that far below zero. In sub and near zero temps, I have found that surgical gloves make a surprising difference.