By listing a non-licensed driver as an excluded driver, they are alleviating risk to the company because they are excluded from coverage. You will see their name listed on the policy due to the driver exclusion endorsement, but as long as they do not have a license, they will not be able to drive. For example, if your father was pulled over or in an accident without his license, he would be processed as a driver without insurance.
This can also result in differing fines and in some cases vehicle impoundment, which is why we encourage any driver on any policy to drive with a valid license.
Depending on your insurance company’s guidelines, your father’s car may need to be re-registered under your name to be listed on the insurance policy.
Best of luck with adding your father’s car!