Or, just don't be a dick. You can easily, and legally, leave a restaurant without leaving a tip -- but most people don't because they feel it is appropriate to

Or, just don't be a dick. You can easily, and legally, leave a restaurant without leaving a tip -- but most people don't because they feel it is appropriate to support the waitstaff financially. It's not hard to sneak into the back door of a movie theater, but most people don't because they realize it's the same as stealing.