I would have no problem with all drivers requiring a defensive driving course every 5 years. Professional qualifications increasingly require continuing professional development, skilled machinery operators require their skills to be revalidated at regular intervals. Labouring on a building site requires a safety certificate in many countries. A car is a lethal weapon in careless hands, and don't get me started on 17 year olds driving a tractor and trailer with a MAM of 31ton on public roads. Compulsory retraining should be accompanied by a medical and eyesight test. The issue of indicating is akin to the issue of daytime driving lights. It is exclusively for the benefit of other drivers around you. The regulations concerning indicator use is quite clear. You owe a duty of care to other road users to obey them.