system
A chat on subreddit /r/NoStupidQuestions
human
Someone who's "stupid enough to tip in these situations" here - 

It's definitely the anxiety.  Specifically, I do it for two anxiety related reasons.  

First is that it gives me anxiety specifically because they're looking right at me when I put the input into the screen.  

Second, and more important, is that since tipping is "expected" at these places, I always feel like I'm lining myself up for some spit in my food or something similar because I'm cutting into their pay if I don't tip.
gpt
Is this at pickup or with delivery? If it’s at the register when you pick it up, steel yourself and choose “No tip”. Every time. Like most people. After a time, you’ll get used to it and stop being anxious. I speak from experience.