I'm proud to say I've done all of these. I think the "drink with co-workers" is a super-good point and I wish more people were more honest about it!
Seriously.
Alcohol is a great evolutionary adaptation, since it allows people to be extremely dour and responsible most of the time, while being able to loosen up with chemical assistance. Countries that are known for their seriousness and work ethic often have a strong drinking culture (e.g. Germany, Japan). There's a Steve Sailer article about this; I can't find it, and the domain is auto-killed upon submission anyway.