Stupid people have rights too. The Supreme Court has ruled the police cannot protect everyone everywhere all of the time so you’re on your own. That can work if you can get yourself a gun for self-protection or live in a safe area in the suburbs where you don’t need one but what about in the cities where it’s not safe? There are at least tow problems with police. One, they may not be available. They may be taking on the bad guys and can’t respond to your urgent call for help. Two, they may mistake you for the problem. No comfort being shot or shackled when you call in the problem but you don’t look like a good guy. Police can try to help but they make mistakes but unlike doctors there are cameras around to record the mistakes.
People who live in cities see the police and they know whats supposed to happen but in addition to not being able to help as fast as needed, a mugging happens really really fast and muggers are just barely smart enough to make sure the police aren’t around so badda-boom, badda-bing, you’re on the ground and the cops ain’t around.