I live in the US where it's customary to tip 15% of the meal cost (before tax charges) on top of your food bill at a restaurant. Some people I know pay 10% if the service was mediocre and 15% if it was good. Most of my friends tip 15% if the service was mediocre and 17-20% if the service was good.
At many restaurants, if you have a large number of diners on one bill, about 8 or more people, the menu will state that they automatically charge a 20% tip on parties of 8 or more.
Lately, we've been to a few restaurants where the service has been not so good. The food will be good, but your drink never gets refilled, you're missing silverware and can't find a server so you have to find an empty table and grab silverware from the settings there, etc. It seems that at the restaurants with the worst service, when the bill comes, the tip has already been pre-printed and entered under the food total, and it's an 18% tip! And this is if there are only 2 or 4 of us. A small number of guests and we shouldn't be getting an automatic tip added to the bill.
Last night, my family and I went to one of these restaurants. We know the service isn't that good, but the food is good. I probably would have tipped 17% anyway because I tend to err or the generous side of tipping unless the service was truly awful. However, the bill came and they'd automatically added an 18% tip! That really made me cringe, so I crossed out the 18% tip (which is legal where we live) and put in a smaller tip (which worked out to about 15.5% because I rounded the dollar number up).
Are others seeing this? Is it a growing trend?