Service industry workers usually make minimum wage, have
no benefits and work mainly for tips. These are typically
students, part-timers working second jobs, or parents
earning extra income. They work on their feet in stressful
environments and customers can be impatient and downright
rude. These workers maintain caring smiles and remain 
attentive, regardless. Tipping 20% rewards them for their 
hard work and acknowledges that these are people who work
hard trying to please us. It is horrible to tip less, because
it actually affects a particular individual's life. Tipping
well is a classic sign of goodness.