In my experience (of marking tens of thousands of 'A' Level biology essays, and of assessing the marking standards of examiners in my teams), yes it's grand to be able to demonstrate your skilful martialling of relevant facts, expressing them clearly and in context and putting everything together into a persuasive and well-balanced and well-structured whole. The problem is how to fairly assess those efforts. We would typically mark an essay out of 20. Each tick represented a well-made point which was relevant and in context. But our marking scheme for each question (ironed out for the paper over a whole two days of meetings), which typically covered two sides of A4, contained upwards of forty or fifty potential marking points. Three of the questions selected by the candidate typically had a part A/part B structure requiring long answers, and the other two were of the "Discuss the theories on the origin of life" type. In addition, the essay had to be balanced across that scheme (you couldn't score all 20 points by leaving out a whole area of discussion that you hadn't thought relevant/hadn't revised/had forgotten about). There was the question of overall quality of the answer (which we assessed somewhat subjectively according to several criteria, such as writing in clear and concise English, diagram accuracy, the avoidance of irrelevancies and blatant errors and giving the essay a cohesive structure), to which we allocated a maximum of three "quality" marks out of the 20. No marks were allocated for neatness, nice handwriting or effort, though we were allowed to dock a mark for sheer bloody unreadability, whilst retaining the brief that we somehow still had to process the damn thing...

Now each of the poor souls who did the marking had to carry all those caveats in their heads, as well as effectively "learning" the marking scheme - and have that sorted for all nine essay questions on the paper (the candidate had to choose five to answer). In a typical summer exam, I would personally mark about four or five hundred scripts and each member of the team about half that number. Almost all of us were working teachers, doing the marking in the evening and at weekends in term time, working to an extremely tight deadline. Essay setting is a grand idea, but, as you can see, there is another side to that coin. We have to be fair to candidates, whose careers or university entrance depends on our getting this right. Setting tasks that only superhumans could assess accurately doesn't serve them at all well.