They do, and almost all countries have a minimum driving age. Some (including where I live) now have compulsory re-testing at intervals after a certain age, and

They do, and almost all countries have a minimum driving age. Some (including where I live) now have compulsory re-testing at intervals after a certain age, and there's the requirement to pass the a practical test to weed out the stupid. Driving while tired is definitely an issue though.