The real question is: in what situation do you not have internet connection OR the server is down.
In this case, it appears the server has been down for a significant number of players. Therefore, many people can't play... even if everything is fine on your end.
If you can't trust that your city will be there tomorrow due to EA's shoddy servers, then there is very little incentive to even play the game. I guess it might happen with a local save as well... but local saves of a game seems like an easier problem to solve.
In this case, it appears the server has been down for a significant number of players. Therefore, many people can't play... even if everything is fine on your end.
Things get worse however. According to one of the links, EA's servers seem to have a corruption issue as well: http://oyster.ignimgs.com/wordpress/stg.ign.com/2013/03/BEvZ...
If you can't trust that your city will be there tomorrow due to EA's shoddy servers, then there is very little incentive to even play the game. I guess it might happen with a local save as well... but local saves of a game seems like an easier problem to solve.