Sin and the Necessity of Contracts

It just occurred to me that the fundamental reason for having to sign contracts is the sinfulness of man.

Contracts presume the sinfulness of man. They are necessary because you need to protect yourself from the sinfulness of the other party: in the eventuality that the other person doesn't do what he promises or that he accuses you of promising something you never promised. In a perfect world where love for God and love for neighbour prevailed, where people were honest and loved each other as God loves them, there would be no need for secular law or contracts or judges or courts of law or prisons.