That's because people know better. Or at least they did when those etiquette books were written.
Who is raising these people? And if they are being raised correctly, why are they still behaving so badly?
Yesterday Douglas Quenqua wrote a piece in the New York Times about how badly behaved people are and the reaction from those who are not. In his words, "the scolds have gotten scoldier."
This is a very old question. Is it appropriate to be rude to someone who is being rude? Or can you sail with dignity above rudeness?
One of my favorite books about this and other etiquette questions is Mark Caldwell's A Short History of Rudeness. Caldwell introduces us to the rudest man of the 20th century: Colonel William d'Alton Mann. He tried to blackmail Emily Post's husband for having a mistress and it backfired on him very badly.
I tried one of the hypothetical questions on a psychologist. If a young man wants all of McDonald's customers to hear Body Count at top volume, is it right? It seems obvious that the answer is no, but in this world gone strange, I've actually read opinions say, well, maybe. The psychologist cut to the crux. "Behavior that enrages will not be tolerated by society for very long."
This is an active version of what Miss Manners wrote:
"In civilization there have to be some restraints. If we followed every impulse, we'd be killing each other." (Quoted at the beginning of Greg Stump's Groove Requiem in the Key of Ski, where Stump juxtaposes Operation Desert Storm with a winter of killer skiing).
I think if these questions are being raised in the Washington Post and the New York Times, maybe people are getting really tired of hearing morons shout down their mobile phones, running into people who are heads down on their iPhones, and having to watch other people's porn.
One of my favorite short stories is Jack Ritchie's For All The Rude People. In it a man walks out of his doctor's office with a fatal prognosis. In his shock, his knowing that he is about to lose his life and his love of that life, he begins to notice the rudeness of other people. In one case, a father and son are denied admittance at a circus because their discount coupon has expired. The man kills the circus ticket taker and leaves a note explaining that the man was killed because he was rude. The good samaritan/killer does this time and time again and by the end a taxicab driver, about to be rude, straightens himself out to be polite, saying you never know to whom you're talking.