[GuB-42]

Personally, for most of my closest friends, I made them at around you age (I am 40).

The reason is simple: I moved when I was 23, to a place where I didn't know anyone. I met people there, we did stuff together, often, because I was very available, because I didn't yet have other people to spend time with, and now we are friends.

If you already have an established group of friends, you are probably less available to make new ones. But if you find yourself in a situation where distance is created, that's when you are the most available to make new friends.