i take it you never have worked in a restaurant before. Let me give you some facts
Restaurants are the product. The servers sell the products. They make the tips, hence why they try to upsell, they treat you as high as the tip they expect you to give them. If they assume you are a bad tipper, then you will receive bad service. A complaint to the manager may get their act straight, but essentially the servers are the salesmen.
Next off. Hourly you got to realize means moot to the servers in general. A lunch rush hour consists of 12-2pm, a dinner rush hour consists of 6-8pm. The majority of the servers are hired and work during their rush hours to receive less of a wait, and in the end make more money. Now after the rush hours, only 2-3 servers are kept on to maintain service. There is no need to keep 20 servers on when no one comes in, so they let them go, or "phase" them to save costs.
Now, why on earth would 8.50 an hour mean to a server if they only are going to work 3 hours that day with no tips? With tips we make substantially more, but that is only the case if the restaurant is busy, and to keep the restaurant busy we must give the best service possible to make people want to come back.
The cooks get paid hourly because lets face it, you need them all there when its slow or busy. Servers work for a shorter amount of time, and when they do they bust there chops for that time. If a server has time to do nothing during rush hour, you may very well know they also are making nothing as well.
Serving is a turnover business, you get as many customers happy and satisfied as you can before rush hour is over, because once rush over is over, you ability to make money is none.
Restaurants know this. Why would they pay servers 8.50 an hour for them only to work 3 hours, to drive their prices to go double the amount, to receive less customers in all, to have less servers because no one is goign to make a living for 8.50 an hour for 3 hours a day.
This is coming from a full time server and a full time student as a chemical engineer. So trust me, im more than capable enough to realize the pros and cons of tipping vs non tipping.
If a server gave you excellent service, and gave you what you want when you want it. Tip them the 20%, they took care of you hand and foot. You are coming to the restaurant for the food, you want the service along with it you have to pay for that as well. If not you can order it for carryout and eat it at your own homes.
If you don't want to tip, then don't expect to get any service either. You may get an order put down and a glass of water, but thats about it.