Originally Posted by G-BOAC
But, yes, I am also surprised at how often it seems they smile back and seem
so pleased - as if nobody has ever said it to them before

I think it's a shame.
Phil
I had a FA who lurks this board PM me and comment on how nice it was to have polite passenger on board.
It seems the "hello, please and thank you" are noticed and appreciated by the FA community simply because they don't happen that often.
This is a most unfortunate symptom of where society as a whole is heading. Does it really hurt anyone to say these things?