Tipping culture in America is essential to keeping the service industry afloat. With most servers clocking in at minimum wage, tips are pretty much the main way that they earn their living. Not only that, but servers, especially bartenders, have to put up with a lot of entitled customers who thrive on being doted on and babied by their waitstaff and if you've ever worked in the service industry, you probably know, that guests who are rich and famous are usually also the worst. One witty bartend…