For the most part people live in their own worlds, I think. It's unusual to find a cashier that actually looks at you or even addresses you when they "serve" you. I think they are 1) bored or 2) self-absorbed. I am continually amazed at the numbers of people I meet that the first thought that crosses their mind when a situation comes up is "how is it going to affect or benefit me?" If it doesn't serve their needs, they're not interested. Stepping outside themselves to consider how it would benefit someone else is outside the scope of their abilities. That's why, I think, that service is becoming a rare commodity.
Unique, I got a good laugh from your "fixin to". Being from the South myself, I say that in day-to-day conversation, which gets some strange looks where I live now. However, like you, I too know the difference between the vernacular and formal business, social, or written English. Interestingly, I have found in some of my civic club experiences that some of the people who have been so reactive to my Southern slang couldn't write a proper sentence if their lives depended on it!