I'd wager it has more to do with ageing population than car accidents caused by non-native driver licenses.
Whether it is ageing or non-native licenses, I think a case can be made for checking that people conform with local expectations for driving skill.
Your "personal experience" is just wrong. They are driving slower because they cannot react fast enough to be safe. It is well understood that old drivers are dangerous, including the ones going 20mph in a 45mph zone.