Good points
Will only disagree in the last comment you made..think about it again; you are viewing this from the inverse angle
In a work of literature you need decide whether the events transpiring occur within a single day / 'x' amount for hours, or within a longer up to vast period of time. For reasons of economy alone (economy in its true Greek meaning), it makes sense that one should not be hindered by realistic day n night cycles. At best, like you said, they are 'forced' to compliment the narrative.
It being the key factor. Narrative. In an RPG you are the author*, you (ideally/to the extent systemically possible) form and control the type and the flow of the narrative. In the book, the author is the author, you are a mere spectator. Just like in movies too.
*we call him "author" for a reason. He/she is the one with authority, the maestro of the narrative's flow and composition (ie the actual ""story"")
So unlike a piece of literature, within an RPG the day n night cycle need not conform (and as such, by definition, in an abstract manner [no one's counting in a book, see economy above]) to the narrative. It can be there independently, it can dictate some additional form of verisimilitude, that in turn you are free to go along with, clash with, or even exploit.
We move from 'dressing' to one extra system ^^
Anyway, lol..
