So as long as they find a reason to do it, why not do it? Only time will tell how Larian looks at our " suggestions". Fact is the main argument for Day/Night cycle for now is that it looks cool.
I would say the main reason is immersion. They could put all the interactable characters to bed, not add any extra night events, etc. and I sitll think it would add something to the game. Night's here, we can't do anything. Time to go to camp and sleep some.
Yes, I am exaggerating a bit, but to have a sense of apssing time does plenty. Same goes for fast travel (it's already on the fast map). Change the teleporters to waysigns and notify the player that your travelling took an hour or two. It's the cheapest option and it could be doe plenty better with some effort, but I still think it would add ot the game.