One should bear in mind that occupations which are tipped, such as servers at restaurants or food delivery drivers, do not simply do it for the minimum wage they earn - the people who work those positions are looking to earn greater than minimum wage. After all, no one would bust up their car for minimum wage when they could simply get another job at minimum wage which doesn't involve busting up their car so much. With these occupations, you should realize that their service is only being compensated so much and it's on the customer to compensate for the rest. If this isn't compensated for, you will either see the wages of servers and drivers rise or you will see them put in an auto-gratuity in the bill (which I know is the case in places like Australia).
Many tipped occupations are paid at a sub-minimum wage in states where tip credit is allowed (I believe only 7 states do not allow tip credit and most of them are in the West, like Washington, Oregon, California, Alaska, and Montana - I forget what the other two are), with the expectation that the server or delivery driver will earn enough tips to meet minimum wage and perhaps then some. To not tip under those conditions for even just regular service is quite immoral, especially as the restaurant will assume the server or driver made a tip and tax them based on that even if they aren't tipped (and it is one hell of a process to prove that you didn't make the tip, to which it's not uncommon for an employer to fire the employee under the notion that if they don't make tips, they aren't performing satisfactory service).
Also, you shouldn't kid yourself - tipping most certainly does create an incentive. You can see this play out along racial lines as I've recorded in an unofficial study I did here during my time delivering pizzas and posted here:
http://tipthepizzaguy.com/discussion/thread.php?num=12915&ip=1
The unfortunate thing about tipping is that because the tip is given at the end of the service as opposed to the beginning, the server or driver providing the service will be inclined to recall from experience the demographics of the customers which tipped them and the customers which didn't and they'll start to think in terms of probability regarding this. After all, the notion that blacks do not tip is prevalent among workers of any tipped occupation and the data I collected shows that, when considered as a collective whole, blacks do not tip for perfectly good service 50% of the time (compared to whites which do not tip for perfectly good service about 8% of the time). This leads servers, drivers, taxi cab drivers, bartenders, and many other tipped occupations to engage in racial profiling for it does actually have an effect on the money they bring home at the end of the night, and this of course is very subliminal for the most part as they'll tend to only provide as much service as is required of them. It's why blacks have complained in the past that it's harder for them to get a cab in New York than a white person (for when a cab driver sees a white and black person calling for a cab, who's he going to pick?). If tips do not create an incentive, you'd have to explain why this dilemma exists for the groups who do not tip and why they tend to be treated with less satisfactory service.
