Imagine two course sections with the following grading schemes:
Section A: 4 assignments worth 5% each for a total of 20%; 35% midterm; 45% final.
Section B: 4 assignments worth 10% each for a total of 40%; 60% final.
In my experience, students often reason: "Section B places more weight on assignments. I can work with my friends and use other resources, and get good marks on the assignments. Therefore it'll be easier to get a good grade in Section B."