We photographers always have to deal with flakes. Thankfully I’ve been lucky not to have too many in the 14 years that I’ve been shooting.
When it’s a complete amateur they may have just lost their nerve. If not and it’s a pattern of behaviour, they will soon burn their bridges with all the photographers in town. When it is a “well known” person, that isn’t necessarily the case.
I was recently going to be working with a porn model who is visiting town. He flaked on me an hour before the shoot. The message came through at 5.45 and it was a bullshit excuse especially since we’d already postponed the shoot for him from the day before. In the same week he’d also flaked on another photographer using similar bullshit excuses. That photographer has just messaged me saying that he’s done it again and was actually really rude about it.
When you fuck photographers around you should know that photographers all talk to each other, even around the world. It doesn’t matter if you have a global profile  (I refuse to use the word famous with him). He will fast get a reputation as being more of a pain in the ass than he’s worth. You’d have to be legitimately famous for me to put up with flaking on me and to get another chance because that would help my career. Not some wannabe.
Obviously the same can be said of models. They talk too. I know I’ve heard from models of bad experiences with unprofessional, gropey, rude or just incompetent photographers. It doesn’t pay to be an asshole.