Wanna know why?
Because in the other cups, it's possible to not be sure right away whether I'm currently drinking out of it or it's empty. So I have to take a second to think and sometimes need to look. So since I only drink coffee in the morning, I know for sure that the mug is always safe. And I've trained myself to just always go right for the mug.
I bet Tom Brady has dozens of little tricks like that.
Tricks win championships.