I worked as a waitress once and depended on tips. I know how much they actually make an hour. I also know that some places if it's a slow day they are told to go home with no hourly pay.
Using the excuse that people under report tips with Uncle Sam for not tipping is just trying to find an excuse for cheapness.
I would like to see waitstaff personnel receive at least minimum wage and then tipping would be on merit. But then prices would have to rise and people would probably just go to Boston Market/McDonalds rather than say Applebees or Chili's.
And using the excuse that the service personnel on a ship are from a third world country and don't deserve more than room and board is an excuse for cheapness too.
Off my soap box.