It's absolutely the built environment. Your Costco example is a clear example. you drive to Costco, you walk in, grab generic packaged goods without needing to really talk to anyone, and then go to the checkout and use the automated kiosk to make your purchase.

There's no reason to have a human interaction, so why would you bother getting to know the cashier? You're never going to build a relationship with the cashier precisely because of the environmental structure.

Contrast that with walking down the street to a local store that one of your neighbors owns. I bet you would already have a relationship unless you chose not to. Why? Because you'd also see them at your kids birthday party, or you'd see them at the bark down the street, or out on a walk.

I made the choice at Costco to not build a relationship with anyone. There's a guy standing at the entrance checking memberships. I've seen him for years. I don't know him. I don't use the automated kiosk if I have several items. I see some of the cashiers for years. I'm cordial but I don't chat them up. One woman who has been there for years chats with me a bit; I'm cordial but don't reciprocate a ton.

There's a corporate supermarket owned by a Dutch multinational not far from me. I see some of the same employees there every week. One of them loves people and recognizes me. I could stand around and chat with him if I wanted. But I don't want to.

I made this choice. Someone who wants to build relationships chats with people. Folks like that chat with people at the grocery store, on the airplane, waiting in line, etc. Often it leads to nothing, occasionally it leads to something. But the point is, they practice it. I don't. The built environment is not stopping it. Not being in a "local store that one of your neighbors owns" has nothing to do with it either. Plenty of relationships are built in corporate chains.