As Frostiken said, protection will always weight more than a weapon that is capable of destroying that protection. The active protection system seems like a great way to defend the tank against RPG's, AGM's and kinetic weapons like tank sabot rounds, but it won't defend the tank against a burst of 30mm fire. Also, you don't always have to completely destroy the tank. A burst of 30mm fire from a A-10C will probably destroy any equipment outside the tank. Like the APS, TIS, GPS, laser, etc. making the tank ineffective in combat.