The threat model for people who think like this is muggers or drug dealers who come up to you on the sidewalk, not drive-by-shootings from a car. This is mostly inaccurate, but when it comes to peoples' fears, few things are rational.
It's probably exacerbated because for people who grow up in low-density areas, the idea that the vast majority of people will just ignore you is a foreign concept. If you're in a small town and you see someone you know & like, you go up to them and chat. If you see someone you don't like, you bully them or get bullied. If you just ignore them, you likely get moved from the "like" to "don't like" category. If you extend this model out from a town of < 10K to a city of 1M, it collapses very quickly, but not before generating some very erroneous predictions.
