I've noticed in friends of mine there being a chasm of a difference between those who have worked in service and those who haven't in regards to their tipping practices. IME folks who have bussed tables, taken orders and done lower-level jobs have a greater appreciation for the work involved and tip more than folks who might have higher paying professional jobs (or buchrim who are just sort of used to scraping by and don't feel indebted to those who serve them). This is also seen regarding tzedaka where the middle class tends to give much more per capita than those in higher tax brackets, at least regarding akum, not sure if I could say the same for the chevre.
That being said, when I lived in Japan for a year I was only too happy to go according to the local minhag and never tip, no reason to encourage a practice that they don't hold by. But in America and davka in NY and other states where there are two minimum wages, one for service employees (
http://www.dol.gov/whd/state/tipped.htm#NewYork) at about $2/hour and a higher one for everyone else, I think the backronym 'To Insure Proper Service' says it all.