I had a long argument with two Americans of the USA variety about tipping. The attitude they displayed about tipping was that it was "criminal" if a customer didn't tip. My argument was that, since I was NOT a party to the employment agreement between business and employee, I had no responsibility to make up any shortfall between minimum wage and what the business was paying the employee.
It was interesting that they felt very strongly that even though you, as a customer, were not part of the the business/employee employment agreement, you still had a moral obligation to ensure that the employees got their due. They could not understand that the employee was a representative of the business and that the charges for service (of whatever kind) to the customer were set by the business by their prices. Any other charges had to be up front (and not called gratuities).
The Americans of the USA variety do not seem to understand that a gratuity is a freely offered gift on the part of the person giving it and it is in no way a requirement to be given. Otherwise, it is not a gratuity.
It seems to me that the attitude towards tipping in the USA makes it one of the tenth world countries where the society has no concept of an employer paying an employee a fair wage for the work being done.
Now, I don't have a problem with tipping (at my discretion) for above and beyond the call of duty service. However, for normal service being provided by a business, it is not appropriate for that business and employees to have an expectation that I make up any shortfall in living wages agreed between business and employee.