Tipping your server at restaurants and similar venues is not only a social custom here in the United States, but also something which is considered to be common courtesy, basic manners. Many people that I have spoken to agree that it is typical to tip between 15 and 20 percent even if the service is not impeccable, but there are some who would argue that there is no need to tip.
That being said, I am not a fan of people who do not tip.
I know too many people in my age group who don't tip. They say that it's because they "shouldn't be responsible to pay the waitress's paycheck." This will never fail to infuriate me, because I myself am a waitress (and honestly just a polite human being). My waiter could slap me across the face and insult my mother and I'd still probably tip him at least 10 percent, because I get it.
Food service is a hard job, and it takes a certain type of personality to do it well. While tipping is expected of customers and doesn't necessarily come as a surprise to the wait staff, it really is very helpful. Working at $9.25 an hour (in Oregon, that is; In Arkansas, Georgia, Minnesota and Wyoming you would only be making $7.25 an hour), as many hours a week as you can, doesn't cover rent, groceries, gas, phone bills, and every other price tag that accompanies being a responsible adult.
Say you work as a waitress five nights a week and make an average of $50 each night. That's $250 extra dollars in addition to your paycheck, and while to some that might be simple pocket change, when you're paying for life while being a waitress, $250 dollars is a huge help.
Now, in some countries, tipping is considered out of place and even insulting. In places such as Japan or Singapore, it's never expected and causes confusion when a customers adds a gratuity to their bill. In many parts of Europe tipping is expected, and is even included in advance on the bill, but in Austria and Germany it is not obligatory, although it isn't turned away.
In the US, however, tipping is so customary because it can be a substantial part of a servers income, and like I said, that extra cash can make a big difference (don't even try the whole "Well you should be working in a higher paying position if you want more money!" thing, that's an entirely different article in and of itself).
The moral of my story is, no, you don't have to tip your server. No one is going to stand over your shoulder and watch what you do or do not write after you ask for the check. BUT tips are helpful, and can be a large part of someone's income. Minimum wage is just that, the minimum. Also, we talk about you back in the kitchen when you don't tip.
