I would imagine you would use it when a human is unable to enforce a contract - for instance when there is no other party who is capable of enforcing it or who

I would imagine you would use it when a human is unable to enforce a contract - for instance when there is no other party who is capable of enforcing it or who the parties agree should enforce it (because it would be too costly or for lack of trust, for instance). Perhaps this occurs when dealing with individuals who are in different countries and the matter is too small? or perhaps while engaging in illegal activities?