wrong.
They measure your ability to retain fact, to use the fact to support assertion or argument, to manipulate retained data, to write and spell lucidly and correctly (or not!) to formulate an opinion and express and support it, to concentrate, to a certain extent they measure your knowledge of the subject in which you are being examined. And all of this under stress...of course i am talking about a good quality exam and not multiple choice dreck.
So how else would you measure what someone has learnt and retained?
Just because someone is physically in a classroom or similar, doesn't mean they have taken in any of the teaching or understood anything let alone able to use it.
In many jobs it can be imperative to be able to retain and use information on the spot without having recourse to any means of looking the answer up.
Exams can also highlight a number of other potential issues as well that could be fundamentally important.
When I was at law school I went to a lecture with a very low attendance rate as an important assignment was due in.
The lecturer spent the first part on a seemingly rather random diversion from what we had been doing. Thought little more about it until exam day and the subject he covered was the first question on the paper and carried a substantial amount of marks. Many people hadn't got a clue what it was actually about.
We saw the lecturer after the exam and he said they had picked the question on purpose from the lecture with the lowest attendance record to catch out those who didn't bother to attend ie either skiving or couldn't manage their time well enough with the assignment due in.
Made little difference to me as I had a full attendance record but had an impact on a lot of people. Similar to the real world, especially in the law, if you don't act responsibly and manage your time properly it can have serious repercussions.
Exams measure knowledge learned and remembered; how else would you know what has been understood & absorbed. They measure the tutor's standard tutoring whereas assessments are just an individuals opinion that may not be the acceptable standard.