I was picking up sushi tonight from one of our go to restaurants. I called it in, drove there, and walked in to pick it up. The host/waiter ran my credit card and handed me my receipt. It had a tip line because it's the same receipt that some one sitting down would get. I drew a line through the tip and wrote the original total. As I was walking out the host/waiter must have picked up my receipt because I heard him scoff that I drew a line through the tip. 

I am a firm believer in tipping your waiters. My baseline tip is 20% and higher for good service. I just didn't think this situation warranted a tip. 

I'd like to know if I'm wrong so I can correct myself in the future. 