Because that's not what he was told to do. He didn't call plays either. Just because he was 100% coachable doesn't mean he wasn't a great player. That's really quite a weird position to take.
I imagine something that's important for a (pure) point guard is being an extension of the coach on the floor, and the sets work best when everyone knows where they're supposed to be at all times, and it enables him to throw the pass INTO the play, like a quarterback.
Stockton wasn't a crutch-leaner, he wasn't weak-willed, and he wasn't whatever garbage it is you're trying to hang around his neck for a reason I cannot understand. It's frankly offensive as a fan of basketball, saying nothing of being a Jazz fan.