Earlier quoted context omitted.
I think the tests are just the colors under which bureaucratic red tape just happens to sail. Anything that creates barriers to entry will result in people being older before they get their licenses and that is where the bulk of the benefit comes from.
Is there any evidence that young drivers are dangerous due to age rather than inexperience?
I don't think teenagers are any less safe than an person with equivalently little experience in normal traffic situations but they are definitively more likely to be less conservative when they do decide to push the limits. There's a difference between navigating a complex intersection and knowing how fast you can/should go on an empty highway.