I agree; it wasn't like everyone was marching in line with their heads down and keeping quiet. It was just the predominant way to act in public: headphones in, eyes down, don't disturb anyone.

I didn't even notice it until I moved when people would actually make eye contact, talk, and be polite. You still pass people with their headphones in and eyes down... but they're not the majority in the smaller, less crowded city.