I think that a lot of those people likely live in a very car dependent, suburban area, and therefore don't get any regular interaction with people outside of their immediate family.

I live in a city, so I have regular infractions with people that I know when I'm out and about: I pop into the butcher shop, coffee shop or green grocer and talk to the employees I know. I walk the dog, and run into friends and acquaintances that live the next neighborhood over, etc. People in rural areas usually have similar sorts of relationships with people in the area.

Contrast that with the suburbs, where neighbors may know each other to say hello to, but not much past that, and it's hard to build any kind of relationship with the barista at the drive-through Starbucks or any employees at the local Kroger superstore.

There are also the people who have bought into the whole define yourself by your work bullshit and they don't value their relationships outside of work.