It seems silly to reject a concept which you have never attempted to implement and for which, therefore, you have no concrete notions as to what it would consume in terms of developmental resources.
Apparently you've forgotten (or written in ignorance) that Larian attempted to incorporate a day/night schedule with NPC schedules in DOS1 but ultimately gave up on account of the complexity, so they know as well as anyone what kind of resources it would require to implement it. The decision to reject it is well informed and not silly.
Now perhaps you think it's silly to reject your day/night cycle "light" version without having scoped out the resources, but that's attacking a straw man. They haven't rejected day/night cycle "light" because of resources, but rather because it's not something that interests them.
So to sum up: They have a particular vision of what a day/night cycle should include. They have attempted to implement such a vision already in DOS1 and know what the implications are and decided against it due to the added complexity. Deciding not to implement that in DOS2 is an informed decision. Deciding not to implement your light version is a philosophical one.
