This article is from India, but ignore that. People being rude to waitstaff is international. I am sure you can relate to seeing people behave badly to waitstaff. This is actually one of the things I use to judge my dates. If my date is rude and condescending to someone who is providing a service, especially food service, he cannot be very bright. It also evidence of personality and character flaws.
It is disgraceful that this is what we have come to. People are now being paid to have basic manners. Basic manners, not highfalutin elements of etiquette, but easy things that we were taught in kindergarten. Manners, courtesy, and politeness are all free. But here we are handing out cash incentives.