When we have too much material to review for the exams, we could lose our focus. Don’t try to let the student to remember everything, it’s impossible and unreasonable. When the we are caught by full of details, we will lost my direction.
Moreover, if the teachers don’t include the content in the exam the students will simply skip them. So it’s much better to cover all the material in the exams or directly delete the content which will not appear in the exam. And then the lecturers will have time to repeat and illustrate thoroughly the most important things. And the students will have more time to think instead of to remember.