>>One of the reasons for including the tip is that when you tip in cash, only the waiter/waitress gets it. The other way, it is often pooled so that the people in the back - cooks, bottle washers, table cleaners, etc also get a piece of the action. Many of them are working just as hard as the waiter to give you good service.
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>I'm not sure how prevalent that it is. The servers are dependent upon the good will of the back-room staff. One who consistently stiffs them will suddenly find his orders appearing late, food cooked not quite to order, etc.
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>I've always paid in cash because my impression is that the credit card companies charge vendors a percentage of each transaction as a processing fee. I could be wrong about this, but I pay cash just in case.

That's true. The percentage is negotiated by each merchant. It used to be a fairly standard 3% for Visa and MasterCard charges and 7% for American Express. (Which is why a lot of places don't take AmEx). Now it's all over the place.