Why not? I'm not implying that grades & honors definitely correlate in any way with whatever it is you are looking for in applicants, but they could.
Additionally, it may be the case that overall you have noticed that attending an elite school has no correlation with success in your program, but that doesn't mean an identifiable subset of elite school candidates do not as well. For example, suppose GPA doesn't correlate by itself, or even a high GPA at an elite school. Yet maybe a super-higher GPA at an elite school does, or Phi Beta Kappa or whatever.
