Maybe they failed math. Maybe they're allergic to metals. Maybe they think all service workers pool all of their tips the world over and each is secretly building a house in the country with their share. For whatever reason, there are tightwads among us who leave the exact same tip for every meal, everywhere, every time. It's true; just ask your favorite waitperson. Which leaves it to us to either drop a few more bills on the table in their wake or risk being seated by the restroom next time.