This is also true of the tube in London - if you talk to a stranger on the morning commute you may as well have peed in their backpack - the response is about the same.

And it can make sense. A lot of people are packed in small space and commuting. Not exactly an uplifting part of the day. I can understand it's considered polite to try to keep quiet.

What's funny is where I live now in Italy (outside of the big tourists areas) is the exact opposite. Any line or idle time you have with random people will become a conversation. It's almost weird to not have a conversation.