Recently while disembarking a lady passenger with a small child held my hand and smiled and said "have you ever heard of random acts of kindness?" and disappeared down the steps. I was left holding a £20 note. I split this with my fellow crew, it certainly does not happen every day (month or year).
I thought that this was a nice gesture, although she paid the company for her ticket she seemed to want to reward and thank us personally for her time with us!
If in the US tips are given without a second thought then maybe they would not mean as much to the tipper or the recipient? It may be seen as rude to decline something small if someone does something unexpected out of genuine kindness and appreciation?
It bought me a drink on my days off and I suppose I'll always remember the passengers smile and appreciation, that's gotta be a good thing in this day and age. Although I wouldn't want every pax tipping me as a genuine "Thank you" does enough for me!!!
