Why is the car owner prohibited from repossessing his/her car when the car is with our client?

Most of our clients are corporate and sometimes they stay with the car for more than a month. If you repossess the car and the client has not cleared with us, the client might take advantage of that and refuse to clear any outstanding arrears. Furthermore, if the vehicle is repossessed and happens it has some dents, the company does not take the responsibility. Handing over the vehicle should be done in our offices only.