Bad Manners and Brimstone

You have it right: it’s just social lubricant in a business conversation.  “How are you today?” is no more a request for health information than “Dear Sir” and “Yours truly” in the salutation and closing of a letter are declarations of fondness and loyalty.  They are all simply social conventions to make interactions gracious.  I like very much how Victoria put it, especially the bolded:

Bear in mind that "How are you?" is not often meant as an actual question that requires a substantive answer, just an acknowledgement that you're a person and not a robot they're going to bark directions at.

Same for “Happy Valentine’s Day” or “have a good weekend” and the like.  In my midwestern city, that is very common, and even to do more than that.

I always sympathize with hosts of radio call in shows. Very often, callers start by asking the hosts how they are or saying something like, “Hey, how’s it going?“ as if they were making a social phone call. I noticed the hosts simply say, “Fine, thanks, what would you like to ask Guest?“ or something like that, although I am sure they are rolling their eyes!

Of course, individuals, and different cultures, have different preferences and conventions about how much is too little or too much.  It can be tricky not to be seen as being either too curt or too intrusive or beating around the bush.

It helps to remember that it’s just social convention and roll with it.  Maybe it would help if you sort of internally translated it into Victoria’s wording, as if they were saying, “You’re a human being, not a robot.”  That’s something that is easy to say “thank you” to.