@mom2and I agree with Oldfort. My point is that listing a person as a driver on a policy does not make them an insured under the policy, an important distinction. Residents of your household should be listed as drivers as they have regular access to your cars, those that do not live with you do not have regular access and do not need to be listed. Listing them really just lets the company know who has regular access and the ability to track their driving record. Since your son does not live with you he does not have regular access to your car so the company does not care about his record. Any time he drives your car you are loaning it to him and your insurance will cover him as a permissive user.
My point was more about knowing the differences between being a listed driver and an insured. The insured has all of the rights granted in the policy while a driver is just that “a driver”. An individual can be both. For example a 17 year old child that lives with you is both a driver and an insured while the nanny that lives with you is just a listed driver. Some of the issues are around uninsured motorist coverage and replacement rental car coverage. Uninsured motorist coverage covers an insured 24/7 for any vehicle (car, bike, scooter, etc.) related accident but only covers a driver while they are driving your car. An example would be your nanny takes the kids for a bike ride and is hit by a hit and run driver. The coverage would apply to the kids but not the nanny as she is not an insured.
I often see this play out when young adults move out on their own (post college) but take the parents car with them. It is common for the parents to keep the car in the parents name and keep it on their insurance. It is less expensive and easier. The problem is, at this point the child is no longer an insured. When an accident happens and the young adult needs to rent a replacement car (if the policy provides for rental coverage) the insurance company is not obligated to pay for the rental changes unless the rental is in an insured’s name and the young adult is not an insured. This is easy when the young adult stays local but if they have moved a state or two away it gets much more challenging for mom or dad to rent the car.