In the US, tips are how most servers are paid. In many cases, their hourly pay is only enough to cover the taxes on their tips. A low tip is interpreted as some

In the US, tips are how most servers are paid. In many cases, their hourly pay is only enough to cover the taxes on their tips. A low tip is interpreted as some degree of insult, up to and including "I am so dissatisfied with the service I received that I don't think you deserve enough money to support yourself". even if I get served a raw steak The waiter did not cook your steak. It's his job to try to resolve the problem if you tell him about it, and how he handles that situation should certainly influence his tip. If I order an expensive bottle of wine... it's completely unrelated to the performance of the waiter That's not necessarily true. Attempting to up-sell is absolutely part of a server's job, and the convention of tipping a percentage of the bill aligns the server's incentives with the restaurant's profits. I'm not saying that the tipping conventions in the US are the best way to pay servers, but I will say that to disregard such a convention if you know about it is rude. I dislike the German convention of attendants with tip trays outside almost every public toilet, but it's my understanding that failing to leave them at least 50 cents is considered quite rude, so I do it.