Indeed, many people are unhappy that this is not an upgraded SimCity of old. Perhaps that would have been a good thing, perhaps not, but that is certainly a different product than what they shipped. Either way, SimCity (2013) is an entirely different game from SimCity 4, even though the name is shared.
I'm not sure to what degree exactly the new SimCity was optimized for multicore, but just a cursory glance suggests that is making use of all 4 cores in my machine. In terms of what they actually shipped to be calculated in the cloud, my guess would be macro-economic and trade conditions, as well as regional dynamics. These require a view of all the data from the region, and are thus best computed live centrally.
I'm not sure to what degree exactly the new SimCity was optimized for multicore, but just a cursory glance suggests that is making use of all 4 cores in my machine. In terms of what they actually shipped to be calculated in the cloud, my guess would be macro-economic and trade conditions, as well as regional dynamics. These require a view of all the data from the region, and are thus best computed live centrally.