Interesting thread - I have noticed that this happens to me fairly frequently as well. Like the OP no noticeable difference in service in other respects such as when boarding (sometimes a lackluster/no welcome compared to other pax when boarding) but upon exit a similar experience. It has happened sufficiently often for me to notice but I've got other things on my mind when flying and this is not something that bothers me.I realize it could be many things including my demeanor but could also be race related - I'm of South Asian descent btw.