Earlier quoted context omitted.
I think it's worth noting that older versions ran completely fine executing the totality of the required code...
Note also that the last version of SimCity was launched in 2003, running on a completely different engine with a completely different simulation model. The Maxis team has talked quite a bit about the challenges in making their agent-based simulation engine, Glassbox, performant on low- and medium-spec PCs.
SimCity is one of those games that would benefit hugely from multi-core computers so I find the whole "We moved core functions to our servers because your computers are too puny" reasoning to be lacking.
It seems obvious that the only reason they moved processing functionality to their servers is because they have to calculate the inter-region stuff which they cannot reliably farm out to untrusted clients.
Basically they decided that the new SimCity would be a "Social" game from the outset and architected around that, the DRM side-effect is just an added "bonus" for Maxis/EA.
Of course many people (Myself included) just want a new single-player SimCity... Hell I would even take the last SimCity with corrected routing and multi-thread support.