A cousin was visiting us in our nice suburb. We had a slow, not-busy road we walked on when we lived there, and we'd wave to anyone; neighbors, vehicles, etc. Our cousin was sort of uncomfortable, and asked "do you know all these people?" I explained that we knew some of them but were just being polite and friendly. She explained that that were she lived (Boston) you just couldn't safely wave at just anybody you passed.
I don't think this occurred to her at the time, but that means she lives in a pretty awful place. Why exactly would it be _dangerous_ to wave at someone in a friendly way? There's only one answer to that question; because you live around violent or unstable people.
Before anyone says I'm just privileged, I've lived in rough areas before, and I can't fathom why anyone would put up with that sort of daily violence, noise and general degradation of quality of life if they otherwise didn't have to. We ultimately ended up moving out of the city just like you said because the crime was getting worse year by year. Do you want some drunk kid blasting his bass right outside your house at 11pm on a weeknight? (for hours, no less) And if you go and try to get him to turn it down there's a significant chance you'll be met with violence? Or people harassing your wife if she's ever "foolish" enough to walk down the street without you? Or to need to explain to your wife "hey, we can't walk through that group of kids, I can't really defend you against more than two attackers." All of these were regular issues for us. Home invasions on our block started ramping up, we knew people who were attacked, shot, killed, just while walking home.
To your point, this wasn't academic. It can be quite the 3rd rail to try to explain _why_ the violence in the city is bad, what is the cause and what is the solution. But when we're talking about my family's safety, I just don't care. I'm not going to live like that, and would have done almost anything to get my family out of that sort of situation. I really can't even fathom people who would write these things off. "Sure, my wife might be murdered and abused in a home invasion, but there are really cool walk-able restaurants!" It's pathological.