To be clear, I'm not saying that there should be no consequences if you distribute a message that I didn't want you to. I'm just saying that I shouldn't be able to stop you from doing so. If you signed a contract saying you wouldn't, and then you do, I should still be able to sue for that, but the existence of such a contract shouldn't let me control your technology to prevent you from breaking it in the first place.

I'm confused, what's the point of the contract that says "you can't do this" if not to legally enforce that you can't do that?

I'm distinguishing between two different meanings of "can't": not allowed vs. not capable. You should be capable of violating NDA/ToS's, but possibly suffer legal consequences if you choose to do so.