Am not too familiar with the Reggae genre and what people do when attending events around Reggae. Of course have some experience and must say: I see the same things as you point out. Friendly atmosphere. Friendly people. And mostly also open people willing to join together with friends and so called event friends (strangers I mean, but friends for the evening) to create a nice evening :)

I have more experience in the dance music segment side of things concerning events, like festivals and even club nights. I can tell you, same thing, most of the time at least (some events are attracting the not so cool people, but many events in my country do). The 'all together' atmosphere is more easily created when large part of the audience are experienced festival enjoyers, ie when the mass isn't showing up. Music can do amazing things!