This is (one of) the logical conclusions of suburban, car-enforced social alienation: if you don't know your neighbors and your neighbors don't know you, then everything that isn't immediately familiar to either party is treated with suspicion. And this holds for the entire "food chain": police who don't live in the areas they patrol, DAs and CPS employees who don't understand their communities, &c. It's civically and socially poisonous.

It would of course be ridiculous to claim that these things don't happen absent of car culture: it's a broader trend than that, and there are suburban areas that buck the trend. But the urban/suburban divide here is stark: I grew up walking to school and riding public transport alone, and it's normal to see kids running around my neighborhood without any supervision. That kind of freedom works because nobody is surprised to see a 6 year old running errands; they're seen doing the same thing every day.