There was no way to coordinate, so you'd talk in school on Thursday and decide about meeting up in so and so's house whose parents were away on Saturday and it would just spread like through some weird subcommunications channel and people would show up and you never knew what to expect because nobody was sure who would show up or when or if...
Then if you were like a couple of lads or gals short someone would be like "I know this dude at so and so adress let's go there!"...
It was spontaneous. I don't think spontaneity has changed much in humans over the past two decades, just the form of it, or perhaps the constraints within which it operates.
It feels less important now, less like an adventure.
Now bring me my defibrillator will you?