What do they do with the information? The threshold in most courses is to be able to pass the next course. The students who won't do that, tend to drop out, or switch to an easier major, of which there are many.

Teachers do tend to change their content and methods if a large number of students are failing exams, but I think it's based more on a hunch, than on hoping that test scores will yield analytical quality data. This is the sense I get from talking to a lot of teachers. My only teaching experience was one semester at a big ten university, a long time ago.