In Sim City case, part of the simulation is run at their servers. Even while playing a private region, lost of aspects of the simulation are affected by the 'world' (other players). So, it´s not _just_ a matter of DRM: online is part of the game (unfortunately). The point is: did the developers decided to do it that way _because_ EA made online DRM mandatory for them, or they did think this way since t=0 ? We´ll probably never know.