Although this was touched on... If someone who is not on the contract is pulled over, there is the possibility that the person would be arrested for GTA.

If you're in the car then this would not be likely, but say your father/Father in law were driving and pulled over. The cop looks at teh liscense, the contract and see the names don't match. Not only would a ticket be forthcoming, but the cop has no way of knowing the car isn't stolen. Big time issues could ensue.

Ultimately, if you choose not to follow the procedures we could come up with a million what-ifs that would be bad for you. How likely each scenario might be is debatable, so it is really a function of how risk-adverse you are...