Written agreements provide more certainty for both parties than verbal agreements. They clearly set out the details of what was agreed.
Provide proof or serve as a record of what was agreed between both the parties.
Give you security and peace of mind by knowing the quantum of work, for how long and what you will be paid.
Set out how a dispute over payments or performance will be resolved.
Confidentiality clauses in written agreement prevent employees, especially those who decide to leave the company, from releasing this information to others for their personal gain. It will also prevent them from competing against the company after leaving.
By making sure that all parties agree on the terms of a particular agreement and making everyone sign a contract attesting to this, this strategy reduces the chance that one party will have grounds for legal action later on.