How are you, stranger?

How has it become an established form of showing one's geniality, by asking "hey, how are you?"...and then walking away before a response is heard?  Or better yet, asking this to a complete stranger, when both parties involved know damn well that the other does not give a single shit.  I understand it is a greeting or acknowledgement of association...but why? 

Each time I am asked one of these counterfeit greetings, it makes me want to microwave a small puppy.  Seeing as this reaction would be severely frowned upon, and hardly worth the pleasure it would bring to me, I instead react in a more socially accepted way.  Here's an example:

The other night, I was standing in line at the supermarket with only a bottle of Exedrin in my hand.  As any decent being with at least half of a functioning brain may have guessed - I had a splitting headache.  Not the dipshit in front of me me though.  He turns around to look at a magazine, see's me standing there, and says "how ya doin?".  My first reaction is of course the mental visualization of myself pushing the "reheat" button on my microwave, as three minutes and fifteen seconds should suffice as enough time to explode a small puppy.  My second reaction is to tell the gentleman that I am doing great, and that I always make trips to the store in the middle of the night to buy pain medication, as it is a hobby of mine.  But then I snap into reality, and realize that this man is clearly interested in my well-being, as he has asked how I am doing.  So I reply "I'm doing okay.  I went to the doctor today and found out that I have an iron deficiency".  He looked at me puzzled, and then turned back around.

By doing this, if I am able to make just one person stop and think "damn, maybe I shouldn't ask how people are", I will have done my job.  Also, small dogs around the world appreciate it.

Why can't things be left as simple as they should be, with a simple "hello", or even better, a smile or nod of the head?  By using one of these "simple" greetings, the best of both worlds are achieved.  From pretentious assholes to benevolent losers, all can be polite without putting up the bullshit facade that they (or you) actually care.  It's a beautiful concept that humanity is too stupid and unwilling to realize.  Unfortunately, humanity is so fucking lazy nowadays, we will more than likely be stuck with the process of acting and asking/answering questions we don't care about for the rest of time.  "Hey, how are you?  Please don't answer, as I do not care"   "I'm doing well, I also do not care how you are, but I'll ask anyways"

Maybe a future controlled by Skynet and their emotionless robots wouldn't be such a bad idea.  In the world of obligatory greetings, less is more.