That's a fair point about tone. In my mind it's the difference, when being asked "Would you like a beer", between answering "No thanks", and "No thanks, I don't

That's a fair point about tone. In my mind it's the difference, when being asked "Would you like a beer", between answering "No thanks", and "No thanks, I don't drink". One says simply no, the other says no, that's something I specifically abstain from. I suppose that could be seen as smug, and the difference would largely be in tone, as you say.