For some, there's the idea of pushing a student to their limit and breaking their boundaries. A student getting 50% on a hard course may learn more and overall perform better in their career than if they were an A student in an easy course. Should they be punished because they didn't game the course and try to get the easy one?
And of course, someone getting 80% in such a course is probably truly the cream of the crop which would go unnoticed in an easy course.
However if that prior is untrue for any reason whatsoever, the normalization would penalize higher performing cohorts (if it were a math course, maybe an engineering student dominated section vs an arts dominated cohort).
So I guess.. it depends
Intuitively and in my experience, course content and exams are generally stable over many years, with only minor modifications as it evolves. Even different professors can sometimes have nearly identical exams for a given course, precisely so as to allow for better comparison.
You’re also ignoring the human element of grading particularly in subjective parts of an exam.
The curving I know at uni was targeting to exmatriculate 45% by the 3rd semester and another 40% of that by the end so the grades were adjusted to where X% would fail each exam. Then your target wasn't understanding the material but being better than half of the students taking it. The problems were complicated and time was severely limited so it wasn't like you could really have a perfect score. Literally 1-2 people would get a perfect score in an exam taken by 1000 people with many exams not having a perfect score.
I was one of the exmatriculated and moving to more standard tests made things much easier since you can learn templates with no real understanding. For example an exam with 5 tasks would have a pool of 10 possible tasks, each with 3-4 variations and after a while the possibilities for variation would become clear so you could make a good guess on what this semesters slight difference will likely be.
