I think that it really may have to do with being from the South, because those standard greetings IMO seem more honestly given. I've gone back and forth between Chicago and the South throughout my life, and in the South, those little formalities seem to have a significant chance of developing into actual short conversations, sometimes even to the point of slowing down the purchase/interaction (of course depending on how busy everybody is, if there's any big news that everybody is familiar with or thinking about currently, etc.)

My theory has always been that it has something to do with the generally well armed/violent nature of the South combined with its sometimes sparse population and resources. You're not likely to meet a ton of new people, some are going to be jumpy/dangerous around you as a new person, and resources (cultural, financial) are so tough to find information about, that it's both important and cheap to spend an extra minute on everybody.

Of course, that's going to be different throughout the South. The protocol is so tight in the sleepy little satellite hamlet/country road (of a slightly less sleepy hamlet) where my grandparents live that you're pretty much expected to wave and smile at every car that passes by, and if you're passing by people who are outdoors when you're driving by, you're expected to wave and smile back. This is not because you all know each other, just how people act there.