Almost one in five men admits to having no close friends, a survey has found

In the past 100 years, as people have moved to the city, and as knowledge has diversified, there's this implicit promise that the city will allow you to find others with your interests. In the earlier years, say at University, this holds true. Young people who don't have many other commitments and are supposed to be there anyway, are able to find their own "tribe". At this time, travel time isn't an issue. As people start having to go to work, and travel time is now utilised for breadwinning, there's not as much time and energy slack left over for maintaining in person relationships. Then having children exacerbates this.

So, now you don't talk to your neighbours because people do not group their housing arrangements around their interests, but around market pressures.

So with sprawl, now everyone has to commute to see their friends. People also have to commute to go about their daily business such as grocery shopping. This means that you can't just "swing by" someone else's house, because they might not be there and you've wasted your time. So we ring ahead. This information sharing to be time efficient became an anxiety of "am I bothering X", which now means those calls don't happen as often either. Now everything has to be scheduled, and anyone who can't fit it in is screwed.

There's also one more keyword which I think isn't mentioned here enough. Career. I have felt guilty at times for doing my utmost to maintain my one free night a week to meet our friends meetup schedule. We shouldn't feel this. The pressure for careers and work cuts too often cuts out the final bit of capacity we have left to maintain even some relationships.

So in summary, people who have common interests are spread out by market forces, increasing commute times, forcing scheduling of time together, and that possibility is then snuffed out by the pressures of needing and income or looking after children.

Rehomogenisation of interests is unlikely to happen, and probably shouldn't. Children aren't going away. So that means the two points to address are: Urban sprawl and career pressures. There needs to be more government oversight that is not completely undermined by corporate interests (I'm sure most large corporations would be more than happy if your work mates were the only human contact you had). That government oversight needs to strengthen the regulations around building of decent apartment complexes, not cash cows, because we want people to live in them, not rush out to the edges of suburbia because they can only afford either a garbage apartment or to move out to the suburban edge. Career pressures are best addressed by increasing people's job mobility. People who are anxious about losing their job do not have mobility. If someones workplace is unreasonable about their time, they're going to frequently be unable to schedule things with friends.

This comes to a point with a family because you have so little extra time that you're very careful to use it wisely. To spend the hours hanging out and getting to know 10 strangers well enough that 1 may become a close friend is just a hard trade-off to make.

As another comment said, it makes one feel selfish. Especially, when that was time you could have spent with your wife and kids. It's hard.

The other thing I think we humans really end up dealing with is being alone. As you age, you simply have fewer and fewer friends. They die. You have less to offer to younger folks and are less mobile to get out. If anything, I think perfecting the ability to make friends would be handy. But I think in doing so, those friends would likely not be "deep" relationships...which gets back again to time.