… quietly boiling bunny rabbits. 
Never did it but many (most?) people would rather avoid an uncomfortable situation with a white lie than confront the situation head on. It’s hurtful and selfish but there you go.
I had it happen to me last week. Was supposed to meet someone from an online dating site in person for coffee as a first meeting. I confirmed it via e-mail 3 hours before the time and she said she would be there. Never showed up, never came back later with an excuse. Still see her profile on the site and it is marked “active within 24 hours”.
Damn, that’s cold.
“If I am not for myself, then who will be for me? And if I am only for myself, then what am I? And if not now, when?”
I guess the answer to that is “when I show up for our date: eye-ee NEVER! Ha ha!”