Wait, what? What form of entitlement are you talking about? People who perform a service for you are entitled to be paid for that service. And waitresses, as if you could be one of only a few hundred people in the civilized world who is ignorant of this fact, do not get paid minimum wages for their service, because as a matter of law, their pay comes primarily from their tips.
You eat, you pay. You get it yourself, you pay only the restaurant. You get served, you pay the person who served you. The fact that the pay is often determined by an honor code that allows you to determine how much you feel the service is worth does not make it any more moral or ethical to skip a waitress’s tip than it would be to fail to pay a doctor or a car mechanic. In fact, if you ever get a 2-for-1 coupon or half off, or something like that, you should consider how much the meal WOULD HAVE cost had it not been discounted.
Back in 1990, I waited on a party of 8. Then, their bill was well over $100, a huge sum at that time. They left me 4 quarters for a tip. The party of 2 in a booth near that table gave me $10 for all the grief they witnessed me undergo.