I lolled reading your bit on the Xmas parties, fucking nailed it. Usually a middle management Bob confessing that everything could be better if only people listened to him too. I generally like going because there are a few people I work with who are pretty cool so we usually find each other and have a good time whenever there's free booze on the company credit card.
Secret Santa is awkward as fuck, but that's part of the fun I think. The ladies get really competitive, last Christmas some of them were on the verge of tears because either they got a really shitty present, or someone "stole" the shit they were after, it's fucking hilarious. My boss got this shitty garden ornament that he visibly fucking hated and spent the rest of the day trying to give it away to people and failing. It's just funny as long as you don't take it seriously.
Good tip on the leaving card, I should try that.
And yeah I agree, it feels like most people here don't work with other people, or not large companies anyway.