"20%? Highway robbery, if you ask me."
20% is not robbery in Manhattan, particularly for an upscale eatery. I waited tables many years ago and was only paid in tips. There are certain cultures and ethnicities that don't understand the concept of tipping. I never liked giving good service and getting nothing in return. I agree with an earlier poster, however, who said that then you can't reflect your feelings about bad service. I prefer controlling my own tipping so that, if I don't like the service, I may leave a dime or a quarter. This way the waiter will know that I am dissatisfied. If he complains, I'll just simply explain. If the 20% is mentioned in the menu, then you can simply choose not to eat at the restaurant or pay. Nothing wrong with that.
The quality or locale of a restaurant shouldn't change the percentage of the tip, since naturally that will reflect in the bill that the percentage is taken out of. It's not like an upscale Manhatten waitress will be making the same amount as a New Jersey IHOP waitress just because they both get tipped the same percentage.
I'm a college professor. I don't get tipped for a good lecture. And believe me, I've tried. ("Bribes," my butt.)