I used to be a waiter for almost 5 years. And the average rate of pay in the United States for a waiter that doesn't have a union to back him up is $2.13 per hour plus tips. Tips are given to the server for the service, not necessarily the food. I can't say how many times I was tipped on food quality and not service though. Sometimes I'd bring a steak that was cooked medium-well instead of medium and get completely stiffed, even after getting them a new steak and discounting the ticket price. There were always a few customers that you could tell were just looking for a reason not to tip you, like when people would try to order things that weren't on the menu, like pancakes and scrambled eggs when it was obvious we didn't serve breakfast in an upper scale steak house, and then they'd tell me, "oh, well your tip just went down."
I've had several different jobs over the years ranging from putting up scafolding, plastering, construction, laying concrete, landscaping, sales, serving, and brokerage. But the most stressfull and demeaning job I've ever had was definitely waiting tables. Imagine having a section of nine different tables, 40 different people, on a busy Friday night, all wanting refills. All 40 people think that they're meals should come first, their drinks should be full, their food should be perfect, and if everything isn't perfect, which it won't be, then they feel that they have the right to demean you, yell at you, call you names, and ultimately insult you by leaving you nothing for your hours of service. As a waiter, you will probably have to tip out a certain percentage of your sales to the bus boy, the hostess, and the bar tender, and possibly the person that sets your food up on the back line. If you don't get a tip from a table, you still have to give a percentage of your sales to all of the people mentioned above, which depletes your $2.13 completely and on a very bad night where the food isn't coming out right and you get flustered, it can see you leave the resturaunt with less than you came in with.
Some nights where everything went right, I could do very well. But a little known secret that I'll tell to all those that have never been in the resturaunt business is that good tippers and bad tippers will always be remembered. It's sort of a self fullfilling prophecy of bad tipping, because when a bad tipper walks in, the whole wait staff will know. The last waiter to wait on them will tell the rest of the wait staff and suddenly that table will get extra bad service, insuring another bad tip. If the customers were very rude, I knew waiters that would go farther than the norm and spit in drinks and soup and other gross things. It's the opposite for extra good tippers, the wait staff will hear about it and will spend more time at the table and will always make sure they are taken extra care of, ensuring that they keep tipping well.
As far as suing for an extra 8% gratuity, that's a bit ridiculous. But let's see, it was an Italian resturaunt and the manager was named Soprano, I think I'd tip well just for safety sake.