Well, not necessarily just "urban" but yes. Going to the other extreme, I've never taken a wilderness medicine course, but I don't believe you are taught to start CPR if you know help is a long, long time away. (This last statement is an important point to get right so someone please correct/clarify if I'm wrong).

I can't find it, but the first news story I read about the change in protocol mentioned a chiropractor in Temecula, California who had already read about compression-only CPR and used it on a guy who collapsed at his gym a couple months ago. He did compression-only CPR for over 12 minutes before help arrived and the guy who collapsed was fine the next day. Impressive--both the result and the effort. (There's no mention of an AED in the article, though, which I assume that the gym would have.)

The important thing is to start early and to keep up those fast, hard compressions to keep the blood circulation going and oxygenating vital organs like the brain and heart. Physiologically, rescue breaths typically take too long to perform and it stops that flow of blood. After giving a couple breaths and going back to compressions, it takes some time for the blood to start flowing again, and every second counts. Psychologically, there's that delay or reluctance that people have about giving mouth-to-mouth, so either CPR is started late or people just don't want to do CPR at all.