Usage rate doesn't count anything magical. The only stats it counts are FGA, FTA and TO. It then tries to adjust for team pace so you can compare players form different teams. That's it. But that doesn't tell you much at all. As far as usage rate is concerned a guy spotting up for 5 shots in the corner on kickouts has been used the same amount as a guy who creates 5 shots for himself up top. A guy leaking out on the break 5 times is "used" the same amount as a guy who posts up 5 times. And those are not at all the same thing. If Derrick Rose takes 10 shots in a game and Kyle Korver takes 10 shots in a game, they have not remotely been the same in their involvement. Does nto even add in assists, which could be used as a crude indicator of amount of time a player had the ball.