I won't dwell on the whole "donation" discussion...I suppose you could test it by putting your total tips given on your 1040 Schedule A and see if the IRS wants to discuss it further with you...

But I will say this: I also tip because it's customary, and I think that's a compelling and important reason to tip. As I mentioned before, waiters, restaurant owners, and diners are all completely aware that the tip is part of the cost model in both the meal price and the labor market. I would much prefer a no-tip culture where the diner isn't the variable, but that's not the case in the U.S.

So the question becomes: if enough of us think the current model sucks, who gets to change it? A few diners doing it is unfair to other diners and the unlucky waiter. Waiters are obviously never going to do it: I think they would almost universally see it against their short-term interests, even if long-term labor demand curves eventually correct for it. Thus the change has to come from restaurant owners. The problem is that, for a given local market, a critical mass of them would need to move to a "no-tip" model somewhat in unison. I'm not aware of this really happening anywhere...yet.

The only time morality plays a role here is advocating and ensuring that the labor market is competitive and fair, with a reasonable degree of government regulation if necessary. The wages paid will be driven by the supply and demand for the skills. Whenever I hear someone complaining about not being paid a "fair" wage, I'm skeptical. Since people are free to accept or decline a job offer, it suggests that the negotiated wage is usually fair...unless there is collusion or some other illegal activity going on to fix the market.