There are a plethora of groups for adults. There are groups for tabletop/board games, music, movies, sports, hiking, etc. There's likely groups near you on meetup.com or facebook groups.
For music specifically there are local scenes. If you go to local places consistently, you'll see some of the same faces. Etc.
I like programming, but I would find it very boring to only be friends with people in the same industry as me.
For meetup.com specifically, maybe, but there are plenty of facebook groups around hobbies that aren't specifically "meetup" oriented. You could look for organizations specifically in your area, and chances are they'll have a facebook group, facebook page for events, or a meetup account.
I also don't see this as an issue. If you want to meet people, that's a great way to do so. I've done it across America and in Korea, and I have made many friends from it.
