Common Courtesy

As I mused in my last post, I tend to hear the word "courtesy" almost exclusively in the phrase "common courtesy."  Historically speaking, this term is very interesting.  "Common," in the Renaissance, meant low and was generally insulting.  If something was common, it was beneath you (assuming you were a literate member of the upper class and leaving a written record of your thoughts).
In this phrase, however, the word common seems to have taken on a sort of low nobility-- if you'll excuse the pun-- and represents not what is low, but what should be inherent in humanity.
Common courtesy, then, is the simple roadmap of rules by which we must relate to each other.
My husband works for FedEx, and one day I was riding along with him while he made his deliveries.  We were delivering a few packages to a store that catered primarily to teenage girls, and there was a small pack of them at the checkout line.  We had to interrupt their purchasing to have the manager sign for the package, and two of the girls rolled their eyes at my hubby (not particularly surprising if you've spent any time around 14-year-olds).  What was surprising is that one of the girls made eye contact with us, smiled and said "how are you today?"  I reflected on her engagement with us, wondering whether someone in her family worked for a delivery company, giving her a sympathetic leaning towards us, or whether she always went out of her way to be nice to people.  Then I realized that it was a little sad that it was such a rare occurrence for someone to exhibit the initiative to be pleasant that I was analyzing the situation.  Surely the dictates of common courtesy prescribe such interactions daily.  The people who many upper-middle class members of society view as "beneath them"-- the blue-collar jobs of delivery drivers, mail carriers, trash collectors, forklift drivers, and even secretaries-- grease the wheels of our society, and we depend on them in many ways.  Surely stepping out of your own world for 15 seconds to say "hello" or "have a nice day" to them doesn't harm us, and it may have a lasting impact on them. 
Common courtesy seems to be associated with respect.  A lack of the most basic of social decorum in daily interactions communicates a lack of respect for a person, and it is this lack of respect that offends us.  We feel that we deserve the respect that we afford others-- the respect of a common humanity and individual choice-- and when we feel that that respect has been violated, it offends us.  I believe that should offend us.  Just as language is an agreed upon group of signs that represent other things, our common courtesies are an agreed-upon group of interactions that determine how we relate to one another.  In an world in which our cultures are becoming more and more integrated, it is important that we understand, expand, and integrate these social interactions as well.  Perhaps the loss of common courtesy that so many bemoan is not a loss after all, but a change in the parameters of what we consider commonly courteous.