This is how things were for the majority of the human timeline. Before mobile phones, people would stop by others homes and just knock and see if they were around.

I understand there wasn't much choice before any kind of phones, but I remember my parents using fixed phone line just fine to arrange visits with friends.

You can always say "I'm busy", and then people go to the next neighbour they like. It's not that bad.

Definitely not a system that produces introverted city coders though

It was a lot of fun when I was younger and didn’t have any responsibilities. You never even needed to go anywhere or spend any money.

I wouldn’t want that now but my school friends always say that if they ever manage to retire early, they’ll all move back to our hometown and do that random hanging out thing all over again.

There are (unmentioned) norms here specific to your friend group. If your friends always come hang on Thursday night, that is about when they will show next week. They probably aren't going to pop by at 6am on Tuesday.