We are generous tippers, also, with pretty much a minimum of 20%, and quite often much more, especially if it is an inexpensive restaurant, since the waitstaff works just as hard, and often harder in those places, for FAR less money, since check totals for meals are so much less.
Maybe it's because when young, I worked at waitressing type jobs, and maybe because both my kids at various period in their lives, did as well, but it's also because we are comfortable financially (although we were just as generous tippers when we weren't), I am grateful that I don't have to work on my feet like that, and we've always believed in "when in doubt, choose generosity".
Those are HARD jobs, and often the people they have to deal with get THEIR jollies and feelings of "being somebody" by mistreating the people serving them. I like to think that we have brightened someone's day, instead.
We tend to tip especially well in "tourist type" places, where most customers are just passing through, because we've noticed that those areas tend to have the largest percentage of people who try to "save" on their vacation costs by tipping miserably or not at all, since they'll "never see these people again".
What goes around, comes around has always been how we operate our lives. It's worked for lots of years now, so don't have any idea of changing. Besides, our feeling is that when we go out to eat, if we don't think we can afford to tip well, we have no business going out to eat in the first place. ;-)