But, in general, oral communication is harder than written. Written form allows you to take time to form sentences, correct mistakes, reorder thoughts, follow an outline... Oral communication, on the other hand, forces you to think and speak in parallel. It's always going to be harder.
In my opinion such examinations and written finals succeed in filtering out people who can only regurgitate what they have been spoon fed in class rather than being able to use that information to move forward. I think I was lucky to study when and where I did, it stood me in good stead in industry.
Of course there are some people who really do find such examinations difficult. In my opinion the solution is to provide assistance to those people to do better rather than throw the baby out with the bath water.
American oratorion is generally awful. Talent in it command a premium. Perhaps this is related to our lack of oral examination ? We’re more comfortable with written argument because that’s how we’re taught to think?