The restriction is on adopting the name and particulars of someone (i.e. fraud or identity theft). It has been explained that holding a driver license is akin to holding a U.S. Merchant Marine ID Card but instead you're a member of the State Merchant Marine sailing seas of asphalt. If you look at most any military or paramilitary dress the LAST NAME tends to be the only thing on the breastplate. When a well-known monarch was worked as an ambulance driver he/she had a last name. When he/she stopped (i.e. retired --has nothing to do with age..retiring is exiting the public service) he/she ceased to have a last name. (Elizabeth Mountbatten-Winsdor was the name Elizabeth worked under).