There is alot more to the game of BB than just being a scorer. Granger is a good player, BUT
he's not a leader
he's not the go to guy
he's not a clutch player
he doesn't make his team mates better
he can't or won't play "D".
He's basically a scorer, and that's about it. There was a reason why he didn't play much in the World games this summer. He can't/won't play "D" thus he got little PT. Coach K played players who could do more than just score.