It's simply because people are generally rude, arrogant, and disrespectful these days, I'm afraid. Fortunately some of us prefer to be polite to Cabin Crew, as I always have been, and have therefore always had the pleasure of a pleasant conversation, laugh and a joke with you guys and gals over the years, and, as a result, I get good service from your good selves.
I cannot understand the mentality of some of my fellow passengers.
But then, I am married to a beautiful woman, comfortably retired, love travelling and flying, so I don't have any reason not to be polite,I guess. Fraid you're aways going to get them,but that's life these days.