Something that hasn't been mentioned and which a lot of people don't know is that in the US servers and bartenders have to pay taxes on their gross sales - it's taken right out of their paycheck - regardless of what tips are made, if any. Plus they declare tips and it's taxed just like the rest of their money. It's not free money or anything. (Although I did work with lots of people that never claimed correctly.)
And most places I ever worked I had to tip out a percentage of my gross sales as well to the bartender, bus boys and kitchen. Not from my tips, but from my sales. Most places worked on the 10% assumption - that you made, in tips, at least 10% of your gross sales. So if people didn't tip, I actually lost money. Cause I still had to tip everyone else out and pay taxes on those sales.
So there's more to it than simply expecting people to tip. I always did my best to give great service, but I got stiffed a few times and had some regulars that never tipped period. When I gave good service and didn't get tipped cause someone didn't "agree with tipping" I told them to stay home or eat fast food. Why should anyone have to pay for someone else to eat out?