I hate it. I swear it's a trap.
You are not just supposed to say, "Fine. And you?" You are supposed to say, "Fine. And you?" and really mean it.
If you are not fine, and say you are not fine, you are being selfish, self-absorbed, and rude.
If you are not fine, and say you are fine, then if the other party messes you over or whatever, they have the built-in excuse of saying, "But you never told me! I asked and everything! I really want to know how you are!"
Either way, unless "Fine" is an honest answer, you're screwed.
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"Alas, our dried voices when we whisper together are quiet and meaningless, as wind in dry grass, or rats' feet over broken glass in our dry cellar." --TS Eliot, "The Hollow Men"