They tip. Very well.
In many other countries around the world, tipping in a restaurant is not a common practice. In America, on the other hand, tipping is the sole method through which workers in the service industry make a living.
In America, restaurant servers are paid extremely low wages by their employers and it’s up to the customer to pay for their service accordingly. In Europe, for instance, employees are paid a generous living wage by the restaurants and therefore do not require to be tipped. Americans tend to feel guilty about not leaving extra money for the server and err on the side of common decency.