In my area, witnesses would throw large parties for every conceivable reason. Lots of graduation parties, wedding anniversaries, goodbye parties, welcome so-and-so parties. I'm not talking small get togethers in someone's backyard. I'm talking rented ballrooms, bands, catered food, etc.
A few hardass elders would crack down in their congregations, but there were so many of them being thrown in neighboring congregations that it was a losing battle. You'd see the same group of JW youth at virtually every one of them. It was a social thing. Word would get out (this was before social media) and some of the local JW youth would use these parties as a substitute for going to your local bar/nightclub.
As I began to drift away from the religion, I discovered that some did not use them simply as a substitute. They would simply head over to the club afterwards. Hell, I would even see groups of JWs at some nightclubs in suits and ties who'd just gotten out of that particular weekend's graduation party, elders kids puffing on cigarettes drinking gin and tonics. That sort of thing.