If a problem arises, a written contract would offer proof of the agreed-upon terms and conditions between the people making the contract (parties). This may be beneficial in a court of law. With some exceptions, a court may not accept evidence about oral terms of the contract if there is a written contract that is complete on its face.  Of note, a person is presumed to know the terms and conditions of the contract and what their responsibilities are when they sign the contract. Never sign a contract or other legal document without understanding what it means.