To me, it seems to be a death by a thousand cuts. Just a few challenges that come to mind:
- The housing crisis has made it very difficult to live close to your friends and just pop in throughout the week.
- Organized religion is in decline and nothing has yet taken its place as a "third place" for a community to congregate.
- Needlessly intense working conditions and / or working remotely has taken away the "second place", where you would typically "hang out" with your co-workers.
- Many people today choose not to have children, starkly dividing adults into mutually exclusive schedules and social personas.
- Many people move frequently throughout their young-adult and early-adult years, fragmenting their social lives and preventing mature friendships from forming.
- There is a significant cultural gap between older and younger generations, creating social friction within the nuclear family unit and across generational boundaries.
- The digital age has moved the location of many common past-times from a public "third place" to your private bedroom.
- etc, etc, etc