It seems so obvious, an inherent part of tackle football, the tackling part. It might even be a key ingredient to being successful. It's a bit complicated, but try to keep up. If a defender gets all the other stuff, the preparation, the schemes, the handling of his specific assignment, the pursuit, the putting himself in proper position to make a play and then … well, bounces off the ball carrier or whiffs on him completely, it's no bueno.
You can't tackle, you can't win tackle football games.
It's like a baker who's baking a cake and forgets to add flour.