Does anybody know why shingles hurt more at night?

This may sound like a ridiculously easy answer, but it is likely because you don't have anything else to do at night but experience the fullness of the pain. Plus, you are, ideally, trying to get to sleep and will be more aware of the distraction of the pain than in the day when other things are going on. It is a possibility that the life cycle of the virus just happens to be one that has increased irritation for your body at that time of day, but I am not familiar with that happening in a zoster eruption (shingles).