Long story short, it doesn't exist for the most part. I visited TGI Friday's here in Taichung last weekend and was amazed by the diligence of the staff. From the time I entered the restaurant, they were completely professional--probably the best service I've ever received in any establishment. Although a service fee is included in the price, I left a tip anyway (which probably confused the waitress who saw it on the table). Service like that deserves to be rewarded.
I wish staff in America had the same attitude as the aformentioned do. I also wish the tip was included in the price. Well, I guess it is at some of the better restaurants but the servers still expect a little extra from the customers regardless of the level of service. If you don't ante up, you risk a confrontation in front of everyone. I've had a few of those, not at restaurants, but in situations where I didn't realize a tip was required. A bus service from the airport and the Best Buy employees who mounted my TV on the wall come to mind. For the latter, I would have thought the $150 charge would cover everything but I guess I was wrong.
I wish anti-tipping clubs would form in the US. Groups could go together to restaurants and other businesses and refuse to tip for bad service or when tipping should not be necessary. They would have strength in numbers and be able to challenge the entitlement mentality there.