[jrockway]

I think this depends on the intimacy of the two people having the conversation. "How are you?" does always yield a (grammatically) direct answer: "great!" "good" "fine, thank you!" "ok...", but which of these someone chooses depends on how much time the other person wants to spend talking about it. You are right that it is uncommon to ask "how are you" because the questioner wants a detailed assessment of your mental health. It is just a set greeting. "I greet you!" would work just as well in many cases.

Not going into any depth here is a proxy for the relationship not being very deep. When I check out with my groceries, "how are you" is always exchanged. I am sure that neither of us really care about the details, so the details aren't discussed. Similarly, the kind of person that you have this superficial relationship with isn't going to give you a special price, invite you to their party, or invest in your startup. That is a deeper relationship that has to be cultivated somehow. That is not unique to English, that's just how people work.

A related issue is how people try to avoid random conversations with strangers. The people you see on the sidewalk walking at a brisk pace, looking at their phone, never making eye contact, wearing noise cancelling headphones are sending a clear message that they do not want to have a random conversation with you.