To me, it's just the difference between city vs. rural in general. I had always heard of something outsiders refer to as "the Seattle Freeze". Essentially, they say we're "polite, but not friendly." I would consider that to be generally true of most major cities, and I've been to plenty of those. It wasn't until recently, however, that I went on my first vacation to the sticks, at which point I really experienced the difference between city folk and urban folk. It's a pretty significant disparity.
That said, I love the city. I probably won't ever leave. But there's really no comparison in terms of immediate hospitality.