This is effectively saying we just shouldn't have copyright. Person A buys a movie and agrees to not distribute it, but goes ahead and does it anyway to Person

This is effectively saying we just shouldn't have copyright. Person A buys a movie and agrees to not distribute it, but goes ahead and does it anyway to Person B. Person B hosts it for everyone, and Persons C through Z get it and also host it. You're suggesting Person A is liable, but the cat's out of the bag and Persons B through Z can continue redistributing it forever because they never agreed to anything. If this is the desired goal, you don't need copyright at all, you can already get Person A on violating Terms of Service or whatever.