Having been in education for ten years, I've seen some real changes - all as dull as a Brexit talk at a vegan dinner party
Just like with the exams themselves, you want a fully-functioning brain in case you have to make an important decision regarding your university choices, clearing or taking a year out.
For some students the retention of subject information is good throughout the year, and therefore they won't need to revise for more than a couple of hours each day. However, there are those that struggle either because they haven't applied themselves effectively throughout the year or because they genuinely find learning harder than other students.
Another factor to consider is what specific subjects do universities require for entry? Obvious ones like Medicine require Biology and Chemistry, not so obvious is Mathematics as a pre-requisite for some Psychology courses.