Latency target says it all. Hard kill of sabot munitions just isn't currently feasible.
Plus, while adding layers of protection to armor (or ships and planes) is a useful endeavor, the maxim of shooting the archer, not the arrow is a better strategy. There's a point of diminishing returns when you layer so much on a vehicle instead of dealing with threats using an entire system (Artillery/Infantry/ECM/ECCM/Air Support).
