Basically, a little nudge far away is plenty, but the closer it gets, the more power is required to move it far enough to miss. But too much force will break it instead of move it. So there's a limit to how close an object can be and have deflection still work. The farther away, the better.

Of course, the farther it is, the harder it is to reach and to calculate exactly how to nudge it.

So there's an optimum range just inside the limit of where we can detect, measure, and reach things.