As long as they are only shooting each other in small isolated areas where the police are too incompetent or uncaring to stop them, who really cares?
Because people are dying? I mean, duh.

I mean sure, there are all sorts of economic reasons...gang violence isloates communities from the city at large, perpetuates an underclass that is expensive and doesn't contribute, violence can leak into other areas, etc...
But really, I would think that "people in my city are getting shot on a regular basis" would be enough to spring to action. Just because people aren't getting shot in my particular neighborhood (very often) doesn't mean that I'm not concerned that people are getting shot in Chicago.