I'm a former restaurant manager and some of the attitudes on here are despicable. How low some of you think of a very valid and very challenging profession! (Fair warning, I'm only speaking of the US in my comments.)
First - most of the anti-tippers have NO idea what a server is expected to do when they walk away from the table. No one has mentioned preparing your (often complicated) salad, preparing your soup, or preparing your desert. No one has mentioned communicating with the kitchen line to ensure your burger/steak is prepared right, that your request to omit an ingredient is fulfilled, or to prod on the line cooks to get the plate out in a reasonable time. No one has mentioned navigating the bottle neck of a kitchen line when her five tables worth of food are queued up behind the OTHER 25 tables in the restaurant. Also, no one has mentioned that there is an equal and equivalent level of server duty when she orders from the bar. And let's not forget about bussing your table, grabbing your child a high chair/bib/crayons, and then cleaning her section (wipe, vacuum, dig into banquette crevices to get the crumbs out, reset the entire table in finer establishments - which includes polishing crystal and silver).
Your server isn't a mindless robot that jabs an order into a screen and waits to pick it up...one table at a time. It's a physically, mentally challenging juggling act - that when done well - must look effortless.
We tip because our society developed the custom at a time when we were willing to recognize the skill and talent of waitstaff. Unfortunately, as our culture became more casual, we never bothered to develop specific norms for the restaurants that fall into the "casual" or "family" categories (table service but fewer courses/options/complications). You may not value the level of service at these establishments as much as a fine steakhouse, but please refresh yourself on what I laid out two paragraphs above. Servers in the US are not paid minimum wage. They are almost universally paid 1/2 the minimum wage in their state.
If you can't appreciate the services a server provides you and if you are not willing to bend to the convention of tipping based on the quality of that service, you have no business sitting at a table in any restaurant and expecting service. And honestly, the McDonald's drive-thru will save you more money over all and provide less mental anguish when the bill doesn't have a tip line.
