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.