"Good" is calibrated to the implicit mapping between "actual merit" and "what the patron would say now" in that context.

It's just like when you ask someone how they're doing. It's not a lie (I claim) to say, "I'm doing fine", even if lots of things in your life suck and are stressing you out, because such a response is interpreted differently than a serious "life analysis" inquiry, and the person asking the question knows this and therefore is not deceived.

I wouldn't say it's "taboo", but rather, a case of using slightly different language in some situations that (knowingly, knowably) conceals a lot of information.