Aside from being one of my major, major pet peeves (using 'k' in English to represent the 'hard C' [k] sound as though alliteration actually requires the same orthographic character), the title of this post is empirically true.
One recent day, on the way into work, a series of people each held the door open for the person following behind. Seriously, three or four people did this in front of me, each checking behind them to see if they should hold the door a little longer. Without even thinking about it, I did the same, and actually contemplated how long it was appropriate to wait for the lady who was quite far behind me -- until she waved me on in.
It's funny how just the act of seeing someone doing something incredibly trivial but considered to be polite causes so many others to modify their behavior in the same way.