On the Big Bang Theory, Sheldon and Leonard have The Roommate Agreement.
One of the rules is The Manners Rule, in which Sheldon states:
At least once a day, I ask how you are, even though I simply don’t care.
There’s a lot to be said for just asking, just as a matter of course, and looking interested in the answer to the question, even if the answer is longer than, “Fine, thanks. You?”
It’s free to ask, and it’s free to listen and it greases the wheels of society a little bit.
Just like a Slattery 
We had a cousin — admittedly, she was developmentally disabled — and you had to remember not to say “How are you?” to her. Because she she would tell you. In excruciating, gruesome detail. You could ask “How have things been?” but “How are you?” was a trigger.
I think most people really harbor thoughts of saying more than that they’re fine. I try to keep it short, myself.