Meeting the "candidate" lets you apply some judgement about them that you can't use from just reading a CV (or just knowing their past GPA). How they look, how

Meeting the "candidate" lets you apply some judgement about them that you can't use from just reading a CV (or just knowing their past GPA). How they look, how they dress, their accent, their body language, etc. People think they can get valuable information from this, so they want to meet the candidates, even if they are told the answers are random. You need to prove (and then convince people) that all this extra information (the impression a person makes when you meet them) doesn't improve your prediction of their future GPA over a prediction based only their past GPA.