Having a low GPA does not indicate that the person spends their time "frittering away on self entertainment via music or finger painting" - it might mean that t

Having a low GPA does not indicate that the person spends their time "frittering away on self entertainment via music or finger painting" - it might mean that they don't waste their time on things that aren't valuable, and focus intensely on what is important - which could be the very skills that would be useful in whatever post-university life they will have. Granted, if you are trying to hire a drone who will mindlessly accomplish whatever they are tasked to do (and will never challenge stupid ideas), perhaps independence and creative thought are the last thing you want, but it's pretty intellectually bankrupt to conclude that anyone who doesn't get good grades is just wasting their time.