Tipping in the US is definitely out of control, but that is no excuse to punish those whose main source of revenue is tips. My favorite example of out of control and unnecessary tipping is the extortion fee used by unionized longshoremen at cruise ports who do little more than move baggage from the trunks of cars to the crates that are sent on board. The crew on board does all the real work. (The porters who help you out of the terminal after the cruise are not included with the longshoremen.)
Even the standards have changed. It used to be 10-15%, with 15% going only to those who truly went beyond reasonable expectations. Who decided that 15% should be a minimum?
While I still believe that those who knowingly stiff the crew on a cruise ship without reason have a special circle of hell reserved just for them, I have to agree with those who say the practice is out of hand in some areas. I don't mind tipping for services that I want or need; paying extra to people who are already being fairly compensated to do their job is fraudulent.