Actually, considering how the game works, I'm 100% convinced that it's the result of EA considering the single-player case... except in EA management lingo that use-case sounds a bit like, "OMG, gazillions of people will pirate our game, or buy it used on EBay."
Seriously, the game IS at heart a single player game. I've managed to squeeze in between server crashes and start a game or two, and guess what? The game functions exactly the same when the server crashes while you're in your city.
The lie that the game is too complex for a single CPU and they need to do server-side processing too, was just that: a lie. The only "server-side processing" they do is saving the game and publishing your game events.
But here's the funny thing: Steam for example manages just fine to send your achievements to the server in the background, without needing the game to be tethered to a server all the time. Skyrim, Fallout New Vegas, A Game Of Dwarves, etc, take your pick, they're all single player games that Steam can both provide DRM for and save the achievements (and for some even the save games) on their server without pretending it's an online game.
So anyway, the game IS perfectly able to run single player. It's not a real client-server product like WoW or EA's own TOR. It doesn't need a server or a server emulator to play exactly the same. It's a single player game, which is perfectly able to function without a server, plus some artificial tethering to their servers that doesn't really add much.
So why IS a single player mode missing at least as an official option to start the game, when the game functions perfectly well in single player?
It seems to me like the only reasonable explanation is that they considered single-player offline mode as something to prevent.