Who walks their dog in a dog park at 1AM? On the other hand, good dog!
The dog has insomnia...
Well, *I* do quite often, since it's: quiet, close to home, there are few others around, and it's a good way to wind down after work.
You *are* aware that not everyone works 9 to 5, right? Many folks work odd hours that can include getting off work at 11 or midnight or 3 am. Where I work we have 4 different shift lengths for the various jobs here, plus 5 different start times. It's not unusual to see a nurse walking out to her car at 0245hrs, or a cook pulling in a 0400.