One of the conceits of cop shows is that there's tremendous pressure from politicians and the public to solve crimes. Unsolved murders are a black mark on police departments and individual detectives, and the press is constantly breathing down their necks for arrests and convictions.
At least here in the urban hellhole, that just isn't the case. We hear about the crimes, but rarely get much follow up. Okay, when it's a certain kind of white person getting killed we might hear more about it, but mostly the stories just disappear and the too often the murders are unsolved.
This is more a criticism of the local press than the cops. They just don't follow these stories from start to finish.