When someone says "How are you?" to me and I don't know them very well, I'm often torn between the polite answer of "Fine", "Good", or other similar answers and the correct answer of answering the question. I don't really think of it as a social noise and more as a method of growing closer. To me, if I ask "How are you?", I'm actually inquiring as to your health because I care and I want a "growing closer".1 There are many other methods of greeting that one can use if you're just interested in being friendly. So, I get a touch annoyed when someone says "How are you?" and doesn't wait for an answer. I frequently try to understand the underpinnings of social rituals. It does help me understand people a bit better and I need what help I can get.
1I can't come up with a better term than 'growing closer'. I'm using it to describe a process of interacting and getting to know someone better such that the social network that we are both a part of grows ever slightly more close.
P.S. I seem to actually have a brain today. The rain this weekend probably helped my allergies as I'm rather clear today.