This is like trying to tell a kid that they have to go to bed at 9 because there's a witch that eats kids who stay up after 9 - but all you want is an extra hour in your day to not deal with them. It's a bullshit explanation that makes exactly no sense. If SimCity offloaded "a significant amount of calculations" are performed in their server cloud, their server cloud would inevitably crash under the weight of even a few hundred or thousand players at once. What calculations could Sim City possibly be doing that it can't handle on a local PC? I understand that there's a lot of stuff going on but modern computers are really quite good at lots of calculations. Having to send the requests to the cloud servers, wait for the server to do calculations, and then send back the results would only succeed at making the game lag to an absurd degree. It's nonsense, and if anyone actually tried to design a mass-market game like that, their software design is broken. If the game they make is so complex that it needs teraFlops of processing power from their servers, then by mighty Thor's beard they should be dedicating their servers to solving the the mysteries of the cosmos, or the cure for cancer, or whatever, not trying to process things for SimCity. But no, obviously it's just DRM and they're trying to cover their asses.
The thing that struck me is that the guys that generally do Folding@Home? Seti@Home? The ones with the herkin' computers that they lend out time on out of altruism? Yeah, generally gamers. So the whole "your poor little computer is inadequate to do the calculations necessary to run what is basically Minecraft XL so we'll take all that stuff internal" is quite possibly the worst lie EA has ever told. And it's kind of amazing that they went with the "we're doing you a favor by keeping your hopelessly inferior machine from having to do math" angle. It's like something from an SNL skit or Archer episode.
Are you familiar with Dwarf Fortress? It's been out for public consumption since about '06 and is frequently updated. Still technically in alpha, if I'm not mistaken. It randomly generates a world which is somewhere between the size of a small metropolis and all of Maine, millions and millions of tiles, spread through around 150 layers of depth by default, a history that generates and changes the entire map one year at a time for potentially hundreds of in-game years, collections of civilizations, a population of up to about 200 dwarves by default (if I'm not mistaken) with I think no specific upper limit of animals, not to mention NPC traders, invaders, monsters, bandits, and so forth, and the numerous moving parts involved in many mechanisms and traps, weather effects, and flowing water. I guess what I'm getting at is yeah, fuck EA's excuse. If a one-man project of love from the early parts of the 2000s can handle that, there is no good reason the calculations for sim city couldn't be handled on one's local machine. And this mod has proven that hypothesis.