If a math wiz can ace their math class without studying I'd question why they're not taking a harder math class. Alternately if the math wiz want to focus more on literature (or whatever else) this semester wouldn't it more efficient to skip the math class entirely?
Maybe in high school or mandatory undergraduate courses I could imagine a rationale for deliberately taking easy courses, but I've encountered students in graduate-level courses at an expensive private university that could have passed the final exam on the first day.
I can't fathom why anyone would waste so much of their own time and money on a class that isn't going to teach them anything.