Students have grown up in a system that has taught them to work for grades. Most teachers are still using grades to incentivize students. The university's culture, ranking system, and credentialing depends on grades. This all creates extraordinary pressure on students. Even if they are ones who already know they thrive on their excitement and passion about the material and the skill and enthusiasm of a good teacher, when the time crunch comes, the pressure to put the time into the graded class is difficult to resist.