Why do people act like your kid's grades are YOUR fault?

Got a note from the teacher that my 10yo is struggling with math. Which okay, fair enough, we'll work on it. But then got comments from two different family members about how "we need to make sure he's studying" like... I'm doing my best? He does his homework, we quiz him, I got him a tutor. At what point is it just his responsibility to care? Anyway rant over. Anyone else deal with this?