Most of the year, I live in a midwestern suburb: 1/3rd of an acre lots as far as the eye can see. I go on a walk every day, but it's rare that I ever actually see a human being during said walk: Everyone is cooped up in their houses. In practice, in most of this suburban life, every bit of human interaction is planned. We drive to commerce, and there we are met by workers with constantly changing schedules, who have minimal connection to the businesses they work in. It's not impossible to make connections in this environment, but it takes actual effort. This makes work the main form of social interaction for many people around me.

Over the summer, however, I spend time in Spain. A town with a population under 200k, and yet far more dense than San Francisco. Streets are narrower, and most errands are less than 10 minutes away, on foot. The pharmacist, the baker, the workers at the restaurant, don't change very much. Since everyone walks, you really get to pass by every neighbor in the building every couple of weeks. The parks and playing ares with children are never close to empty, and people tend to have routines, so it's far easier to get to know people from random interactions. It's not uncommon to meet people you know, completely by accident, just because you walk the same streets. I might not stop at a certain coffee shop, but it has seating outside, and friends are be sitting there, and therefore I get a chance social encounter, even when I am not visiting the same business. There's benches in random streets, and people meet there, and chat on the street, so you don't even need a business as a "third place", when you have the street. Thus, getting six non-work social interactions a day becomes trivial.

Large parts of America have chosen forms of development that are naturally isolating: It's no surprise so many feel isolated!