Learned this lesson as well as I’m approaching 30. Friendship just won’t automatically happen anymore. It requires your effort and also your friends effort. If you don’t maintain it, it will eventually die down because people are busy and move on with their life.
It will automatically happen if you have shared social space. However that shared social space isn’t automatic like it was when we were kids in school. In school we had a little community and we were there every day. In adult life all we automatically have like that is the workplace. (And of course people are pushing for more and more remote because who needs mental health)
So yeah. The most valuable effort isn’t so much to reach out and try to spark friendship, but to get off your butt and go to that weekly game night.
I will say that when I joined a league soccer team I had instant friends. Sports are amazing for that.