It seems to me that not everyone gets “how are you?”. Do you get it? Are we on the same page here?
To me, it can be used in 2 different situations, with 2 different true meanings.
Situation A is the simple greeting. In this case, it’s not really a question that expects an answer. For example, this exchange is perfectly normal:
Person A: “How are you?”
Me: “Hey.” or “Hi.” or “What’s happening.” with the inflection of a statement rather than a question. I think the “How are you” can also be said with the inflection of a statement to make it more clear that it’s only a greeting.
This seems obvious to me, but I have had people seem offended that I did not answer their “question” to me of “how are you?” even though I very clearly and obviously acknowledged/greeted them, in some way or another.
However, in situation B it is an actual question, but it has a more implicit meaning. Situation B is when you run into someone you are reasonably familiar with, and have a real, vested interest in some aspect of their life because it relates to your own and you want to have a conversation about it.
Person B: “Hey you!”
Me: “Hey person B!”
Maybe I haven’t seen Person B in a while, depending on the relationship perhaps a hug or a handshake is in order.
Now, that the greeting stage is officially out of the way, I say:
“So how are you?”
Here it is a question, but with the implicit assumption of meaning: “So tell me about what you are doing now, or what’s on your mind, or whatever common interest or activity we share that caused us to meet each other in the first place.”
So when people say “I’m good!” or “Great!” or “Fine, thank you.” and leave it at that, without offering anything further, I get the feeling either they don’t get it, or just don’t want to talk to me. Usually it seems more like they want to talk but are just afraid of being the first one to start sharing personal stuff. So I either have to come up with some more pointed questions, or start sharing first. But there must be at least some people that get it, right?