You'll get lots of different answers to this question, and most or all will be right. Since I'm a OneWorld person, the only airline I fly in the U.S. is AA. Unions and the APFA have a lot to do with it. AA cabin crew is required to do exactly what their contract specifies and no more. Another factor is the total lack of onboard management. No one is in charge of cabin crew on a flight, and if someone doesn't feel like working as hard as the others, the only thing that other cabin crew can do is report it after the flight. Obviously, social pressure prevents that from happening.