> To avoid any legal liability. Stating a specific reason would open them to possible "breach of contract" depending on whether the act(s) were significant enough or justifiable, based on the contract terms.
This is how it works for at-will employment, but it would be a very weird contract that allows backing out only if you don't say why you're backing out.
Let's say Caesars states, "we just got hacked and, as has been reported in every major newspaper, paid $10 million as ransom. We have reason to believe one or more attendees of DEF CON were part of that group."
How does making this statement this benefit Caesars in any way? Now DEF CON can demand some proof of this claim, or sue for defamation, or state that without proof, Caesars isn't acting in good faith, whatever.
Yes, most likely. That's why it would make zero sense for Caesars to state anything publicly that would antagonize members of the community. Saying nothing (or even praising DEF CON, and claiming it was a "change in strategy") is the smarter route.
This is how it works for at-will employment, but it would be a very weird contract that allows backing out only if you don't say why you're backing out.