People are pissed because it's an artificial restriction. People understand that talking to a server is necessary for an MMO to work, and they also understand it is not necessary for SimCity to work.

When an MMO talks to a server. it's in the user's best interest. When SimCity tries to talk to a server, it's against the user's best interest, who might want to play in a place without an internet connection, but is prevented to do so by a system that does nothing for him or her to begin with. It's weird that this is not obvious.