Idiocy. If I can set my region to private and never interact with other people, then there's no reason I shouldn't be able to lose the internet connection requirement while doing so. None of your "designed to be connected from the ground up" means anything at that point.
Not to mention what others have already said, that someone who wants a good single player experience probably has no interest in leaderboards or mayoral standings.
I'd love for this game to tank, and for the developers (and publisher) to recognize that lots of people don't need or want multiplayer components strapped into their single player game, but even if it did tank, I'm sure they'd find another scapegoat to blame.