There is a lot of contentious discourse about tipping these days. I believe there's some merit to the idea that you should not have to tip after every transaction. However, if you're sitting down and being served by a waiter, it is your duty (at least if you're an American) to tip your server.
Dine-in movie theaters are one of those places where the lines are a little blurred with tipping, but not that much. Having to come into an environment where you can barely see people's faces and serve them a full meal in a timely manner takes a lot of skill. I know many people don't like the constant interruption of dine-in movie theaters, but I'm sure the waiters hate it much more than any customer could. One customer at such a theater decided to explain why they didn't tip their server, and it is more absurd than you could ever guess.