Then my manager quit. Or a power-hungry executive starts targeting your area, creating chaos. Or the company doesn't raise the funding it needs.
So, you quit, or get laid off, or fired. That family culture, and friends you saw every day and bonded with are either no where to be seen or the dynamic shifts so dramatically it becomes practically unbearable.
Each job I seem to stay in touch with 1 or 2 coworkers regularly, and am on good terms with a few dozen more. But in terms meeting your social needs, it ends up hurting a lot more when you realize you were all alone the entire time and your coworkers were just paid to talk to you.
This is part of why you see a lot more people in their 20s attending company functions or working in startup "family" cultures, and fewer in their 30s, 40s, or 50.
It's good that you're finding something to help address your loneliness. I would encourage you to try to find a few work friendships that you can take offline and outside of work to start building a social network that's divorced from where you're working. And if you have a difficult time doing that, then that's particularly a skill you should work on developing -- because as someone in my mid-30s, it's only going to get harder to make and maintain friendships from here on out.