I use to wait tables about 8 years ago (so grateful not to be doing it now) it just popped in my head to ask this question. Everybody knows the concept of going to a restaurant waiter/waitress taking care of you and you are supposed to leave a tip. Do you really understand that counting on your tips is a apart of the salary. They are paid under minimum wage. Just like when you go to work and expect your paycheck every week waitstaff need their money. Being a waiter is one of the hardest working jobs there is it's physically demanding at certain types of restaurants.
It's so messed up to work hard for a table especially a group and not get any tip. To the 1 dollar or 2 dollars tippers is bad but at least it's something.
The first thing a lot of people want to say is bad service but there are a lot of things that go on in a restaurant that you may not be aware of (especially if you never worked at one)that may cause problems for a waiter. For the most part cooking errors, messed up orders, lack of staff, call offs, running out of things, disorganization. That waiter/waitress is working hard for you if you believe it or not because she/he needs the tip. Next time you're at a restaurant and things may not being going smoothly remember it may not be their fault. Or if your one of those people who just don't care and don't do it just because, really think about if it was you or your husband or wife trying to take of your household. People who have never waited tables before will never understand it's such a slap in the face.