It's likely a personal space thing, which is interesting to me because as an American one of the hardest things to adjust to in other countries when I travel is, typically, their (natural) violation of my norms of personal space. It's something that drives me batty. I hadn't really considered that other Europeans might even have larger norms of personal space, because in most foreign countries I've been to, I've always felt like I'm the weirdo getting uncomfortable when my norms of space are always violated. It is really something I stress out about, and I don't stress out about much.