In the US the minimum wage and therefore all wages payed to servers are lower the the standard minimum the reason is because a portion of their earnings is supposed to come from tips.
These days a lot of guests tend to refuse to pay tips even when the server performed well or even very well.For this reason many restaurants add an automatic gratuity to larger parties it always says this on the receipt(which the one that the pastor left the note on so they did pay the tip anyway).They place the message on the receipt so that the customer can choose to pay the server an additional tip above the automatic gratuity.
There are certainly crappy servers out there but there are also a lot of very good ones that do deserve a fair tip.People usually do not realize that a server is managing several tables at one time so if they are doing very good job they are putting a lot of effort into it.
http://www.dol.gov/whd/state/tipped.htm
food service wage the 3rd raw is what the person gets from the employer.The federal minimum is $2.13 in other words a huge amount of their earnings are from tips no matter how long they have worked somewhere becuase as thier wage goes up it is still going to much lower than someone that started at the standard minimum wage.
How many people get a much better guaranteed wage but put little effort into their work yet have no fear of not earning due to lousy performance?