I've never really liked day/night cycles in games, ever since Ocarina of Time, which was the first one I saw. Fun during the day, plagued by skeletons all night.
Hardly any games do it realistically anyway. Night is exactly the same as day except everything has a dark blue tint. Hollywoood night. Give me blue skies and good visibility, thanks.
I hate this argument, frankly.
"IF D/N isn't super-complex then it's pointless". I strongly disagree, I think it's dismissive nonsense.
It does a freaking ton even when implemented in the most basic form, I'd say.
Even in absence of complex, Ultima-like NPC scheduling, the day/night cycle in BG can enhance the experience significantly:
- it maintain the illusion of the fictional world being a simulated and persistent environment.
- it offers cosmetic variety
- it creates occasions for differentiating factors even in already-explored areas, through a rotation of population/potential encounters (i.e. day-exclusive or night-exclusive monsters).
- it opens to context-exclusive scenarios
- it sets the mood for certain scenes and encounters
Random example: Imagine roaming the streets of the city stuck in a permanent noon and contrast it with having the option to navigate both its crowded market during the day and its dark alleys during the night, or seeing street lights being turned on at dusk as it gets darker gradually, etc, etc..