Here in America, tipping is socially required. However it is not an exact science. Esquire created a list of six reasons that tipping should be outlawed in America and it makes a lot of sense.
Did a server work less because I ordered a $40 bottle of wine than if I had ordered a $400 one?Tipping by percentage is a hard thing but you can't tip a flat rate either. Many people will tip a dollar every time they order a drink at the bar even if the drink only cost $1.
Michael Lynn, a professor at Cornell's School of Hotel Administration, has spent his career researching tipping behaviors, and found that perceived service quality only accounts for two percent of the variation between tips. Two percent!Many people, myself included, claim to tip more if the waiter/waitress is good. However studies show that the difference is only 2%.
Read the full article, Why Tipping Should Be Illegal at Esquire.