If you regularly drive a vehicle that you do not own it is still in your best interest to make sure there is insurance coverage in place.
Liability insurance coverage is required to drive in every state.
For example, in the state of Texas there has to be some evidence of insurance on the vehicle to avoid penalties. With their new TexasSure program it is the owner of the vehicle that is the one responsible for providing verification of insurance coverage.
If you are driving a vehicle on a regular basis that is owned by someone else, insurance companies require that you be listed on their policy. If you are not listed and are a regular driver, they could deny coverage in the case of an accident.
If you are driving a vehicle and the owner of the vehicle does not list you on their policy and refuses to give you any information in regard to the insurance coverage (if any) for the vehicle it would be wise to purchase a non-owner insurance policy.
A non-owner policy provides insurance coverage for you on any vehicle that you drive. You do not have to own a vehicle to be able to get this coverage and it is usually a very cheap policy.
Even if you are not the owner of the vehicle it is prudent for you to make sure that there is insurance in place. In some states both the driver of the vehicle and the owner of the vehicle will be ticketed for no insurance if there is an accident or the driver is pulled over.