I'm saying this hesitantly, because it has the potential for things to go off the rails into a flame war, but the rockets are very inaccurate -- literally hitting the side of a barn would be a good strike. Damaging them probably reduces the chances of them hitting a high-value target by a few percentage points, but they have no targeting systems on board. They are flung in a general area, and landing in place X or place Y in that general area isn't too much different.

There are also significant psychological factors at play.