As someone who used to support themselves waiting tables, it can be very offensive how some people treat tipping. You are not renting a servant, you are paying a gratuity for the use of the table, for having someone bring you food and water, and you better be exactly as gracious as you expect them to be. There was always at least one customer who loved the idea of deciding what your salary for the evening would be, and who would push you to break and freak out on them.
Some restaurants have pushed to end tipping entirely, and instead charge more to cover an appropriate salary for their staff. This has been met with pushback—folks want to decide how much the person bringing their apps get paid! Some servers think they can make more money through tipping. But one restaurant in southern England has reportedly gone so far as to demand that servers pay them to work.
The Bristol Post reports that a restaurant called Aqua Italia is in big trouble for their controversial payment system. Allegedly, waiters have to give management three percent of their bills for the night, essentially renting tables in order to earn money. That cash generally comes out of their tips. So, if you had a customer spend a lot of money on food, but tip abysmally, you'd still have to pay the three percent on their bill.