People often forget how important person to person interaction can be in the moment and for future occasions and, of course, manners in general seem to be in decline across the board. It doesn't take long or any real effort to show some gratitude but the benefit that can come from it is huge.
People have their own scenarios to work around and they sometimes exert pressure which can cause them to focus on their own needs rather than others, and therefore bring less than optimal performance/manners etc. it's a shame really, but it's a human thing I guess.