I think one big problem is that moving to another house is difficult.

The traditional society would have you live among your relatives. Which can be great if your relatives are great, and can be horrible if your relatives are horrible.

The modern society allows you to choose the place where you live freely... at least in theory. In practice, I think if you would ask most people how far they live from their best friends, and how far they would prefer to live from their best friends, those would be two very different numbers. So somehow the relative freedom is big enough to break extended families apart, but not big enough to bring best friends together. So instead of trading relatives for friends, we are trading relatives mostly for loneliness.

There are reasons why this happens. Buying a new house is expensive, and moving to the new house is a lot of work, so you only do it once or twice in your life. The moment when you decide to buy a house, and when you have enough money to do it, is not the same moment when your friend decides to buy a house and has enough money to do it. Despite enjoying the idea of living closer to each other, each of you probably has a strong opinion about the best place to live, and very likely it is not the same place. Etc. Every step in this chain is so logical... and yet, at the end, the outcome is unsatisfactory. Maybe we also suck as predicting what will make us happy in life.

Once I lived in a 10-minute walking distance from my best friend. It was amazing; I never felt so connected socially. Any day, any hour, I could just pick up my phone, ask "hey, would you like to meet now", and if yes, then in 10 minutes I could be with my friend. We talked a lot and played a lot of computer games, heh. It makes a large difference when it is 8PM, and you have to go to work the next day, and still you can insert an hour or two of human interaction if you need it.

These days my best friends live between 30 minutes and 2 hours away from me. It absolutely does not have the same dynamic. Visiting them is something that needs to be planned; for the more distant ones it is something that takes the whole day (2 hours there, 2 hours back, and we better spend a few hours together otherwise it was more traveling than socializing). I can no longer just do it spontaneously at the end of the working day. I need a large time interval, they need a large time intervals, and we have to coordinate these time intervals. So at the end, we meet more rarely than we would prefer to.

Now imagine the opposite situation, if somehow magically we could just live downstairs from each other, or across the street. We could meet anytime. Even anytime we go with kids to the playground, we could meet and talk there.

In theory, there is nothing preventing me and my best friends to coordinate and buy houses in the same city, on the same street. But in practice, almost no one does this. It would take money and time, you would have to sacrifice some of your preferences, you are not sure that the same people will be your best friends 10 years later, you do not want to move every 10 years to follow your new friendships, your best friends are not the same people as your partner's best friends, etc.

So we keep dreaming about something that feels like the right thing, but most likely we will never have it.

I wonder how much the society would be different if houses were like Lego bricks, and you could anytime relatively cheaply move your house from place A to place B (and if you change your mind later, move it back). Whenever you feel alone, if there is at least one person you would prefer to be with, move closer to them.