After university, I moved to a new city where a bunch of my friends had moved after graduating as well. For a couple of years things were really good, but it was a city with a crazy high housing and rental market and my salary was not really keeping up. I also wasn't having any luck dating and just felt out of place in the city.
I made the hard decision to move away for a cheaper housing market and better salaries, even if it meant leaving my friends behind. It's been five years since then and I have a longterm girlfriend, a house of my own, and double the salary I was making. The only thing missing is my friends, and I haven't made many friends here. Certainly not a consistent group to gather with for board games or whatnot.
I keep in touch with some of my old friends online but mostly don't. I think something this article doesn't mention is that sometimes people are just friends because of proximity, out of convenience. It's the ones who don't live nearby but you still want to visit and spend time with, those are your real friends.