Having been to pretty much every significant Linux conference:
The honest answer is that drinking is a significant part of certain socialising, and part of that is down to the community generally being relatively young, spending much of their life working in stressful environments and having the opportunity to blow off some steam with their peers. However, that's not the major aspect of it. The vast majority of well-organised social events function as, well, social events. There may be alcohol available. Some people may drink more of it than is strictly necessary or appropriate. But even if you don't drink (and I haven't at various points in my life), there's the opportunity to spend time with interesting people and have fascinating conversations with them. Not wanting to drink isn't a social stigma, and I'd hope that any encouragement to engage in any kind of drinking culture when you're unwilling to would be deemed as inappropriate as any of the acts in the parent article.