Adults don't ever want to just do stuff. As a kid, you could just ask the kid next door if they wanted to play, and that was your afternoon.
You can't really do that as an adult. You can't ask people if they're up for doing a hobby project together and expect a yes.
Even at the hacker/maker space I hang out at, it's just a gathering of people doing various solo projects. The only group activities I see are people taking courses.
Why are we so dull?