Getting a 43% average in a course doesn't mean you learned 43% of what was expected of you. Did you know that mathematically inclined professors (like in engineering) know that if the grade distribution is compressed up at the top of the range, with 15% of the class getting 100%, then you are clipping off a section of the distribution. You can't actually distinguish the good students from the stars. If you want to be able to see the full range of student ability then your grade distribution should have a tail at the high end as well as the low. That means lower averages.

Additionally, a harder exam will challenge all students. If you get a perfect score on an exam you might feel good, but you haven't actually learned how much you know the material. You just know you know it better than you were tested on.

A 43% was a B+? So the class was graded on a curve and you didn't like the numerical value that you got? Cry me a river.