I think this is exactly the point the article is making here. He doesn't _criticise_ Americans for not saying "You're welcome" - he calls that "over-effusive politeness". Saying that "no great joy" has been found in some service is practically a paraphrase of your "things that were done as a matter of course and deserve no thanks". You are assuming he's being negative, I think he's just being plain.

I went to America for the first time earlier this year, having grown up in the UK I found the "mmm-hmm" thing quite suprising. I agree though that thanking every sales person you see in your day for every small service is somewhat ridiculous.