I remember a never ending discussion when I was in college about why the premeds tended to get better average grades in organic chemistry than the chemistry majors, even though the chemistry majors seemed to have a much better grasp of the material.
I would call that the pathological case rather than the average one. Maximizing grades against learning as little as possible is the lowest hurdle you can cross while still technically being successful as a student.
It's also worth remembering that "student" does not always mean "child currently undergoing mandatory education". I would think that adults who return to complete their diplomas/degrees or add a graduate-level program on top of the undergraduate one are comparatively more likely to choose to maximize knowledge rather than just grades. It's mostly commonly expressed as "now that I'm personally paying for it, I want to get my money's worth".
This was not my experience as an undergrad. I needed a B average to keep my scholarship, so I made sure that was never at risk. Beyond that, I focused on learning and on learning what I was interested in. I spent vast amounts of time on math and computer classes and read as much as time permitted beyond the required materials. On the other hand, I only did the minimum to get the B when I had to fulfill requirements in humanities.