Ignoring the kill mechanism any KE system has to get to the targets before they get into a fatal (kill zone PK > whatever dependent on cost and availability) capacity. Historically this is remarkably difficult; targets are usually much bigger than interceptors and have more cost price vulnerability, Consider 1 hummer + a system capable of intercepting 20 drones (unlikely from the model shown) at 75%. That leaves 5 drones free to play.
And 20 drones probably cost much less than the defensive kit which is now useless. Usually air defence systems work on two factors; planes and training cost much more than missiles, and bods become somewhat constrained in their actions if they think they are going to get twatted.
Neither of these factors apply to drones.
So the equation changes again.