Yes they do.

As for credit card discount, any restaurant will bury that cost in the price of their food. So their discounts are covered one way or another.

As for wages and tips, here in Washington I pay my wait staff minimum wage PLUS their tips. Some of the servers in my place make a hell of a lot of money!! There are times when I think I am going to start serving! They also get ALL of their tip off a credit card. They earned that money and credit card discounts are part of doing business. The business can cover that in other ways without taking from already hard working employees.