I do agree with you, and I also find it extremely annoying that I am expected to give a tip.
However, when I go to the US I know their society works like that, I am visiting and I respect their customs, regardless of how idiotic they seem to me, I just treat the tip as part of the price and there's that.
What I really find annoying of waiters in the US is that they know you'll give them a tip and attempt to their best to be servicing with you all the time. Asking you several times if all is good, you need something else and so on.
I remember once I took a beer with my girlfriend in a bar and before I got to drinking half of that I was asked by 3 different waiters if everything was alright several times as well as being asked twice if I wanted another beer.
Fuck off guys, if I want something I'll ask you. You're not being kind by doing all this, just annoying.