SimCity was a controversial release for EA, primarily due to the game needing to be connected to the internet at all times. Customers complained about not being able to access servers, experiencing lag, and generally being an inconvenience. Though the game itself was generally well received, many feel the game suffered due to this always-online feature.
However, as shown in this post on Reddit, there’s a chance that EA are considering implementing an offline mode in the future. In a survey sent out to customers, EA listed an offline option as a feature that players could express interest in implementation.