I didn’t see mention there of transient living situations as a factor. It used to be far more common for families to settle down in one place and live there until they sold the home as grandparents.
It’s generational. The younger generations have no concept of neighborhoods or neighborliness. They grew up on computers talking to people all over the world who are their “friends”. They have no interest in the person living next door to them and actually feel like having to interact with them is an intrusion into their privacy.