A lot of it is learned behaviour. You get used to working and being productive at night because it's often when you have free time and quiet time. Your brain then starts associating that light setting/environment with 'in the zone' mental states.
As an example I used to be a midnight owl but now with kids I have to make the most of my daytime hours and squeeze as much sleep as I can in the night hours. I totally get the warmth of working the night hours but I am also fine with being in the zone during the daytime. You can shape your brain to get used to anything.
