In order to prevent excessive employee mobility. If you don't sign a contract or make an agreement, I'm afraid that employees will often resign. But after signing the contract, the employees have the contract in hand. If they do not pay wages, it can also be used as a basis for suing them.
Labor Contract Law
Article 37 A worker may terminate his labor contract by giving a written notice to the employing unit 30 days in advance. The laborer may terminate the labor contract by notifying the employing unit three days in advance during the probation period.
