what you call somoeone who has gotten their driver's licence, and has a car sitting at home that nobody uses, but they still don't drive. This is usually because their parents don't trust their driving ability, because they didn't drive often when they had their learner's permit. This is ridiculous because by getting their driver's licence, this person is demonstrating to the state, and thus his parents that he/she is a competent driver. Also, sometimes they are just to stupid/lazy/inconsiderate/unconfident to argue with his/her parents and is content to not drive.
Brian, your family has four cars and only three drivers, so why don't you ever drive?
Either I am not confident enough to or my parents wont let me.