Why bone plating

Because shit like tank karma toplane are a thing and there needed to be more actually tankyness in the tank tree that wasn't conditional on your actions. Having all your tank stats tied to a capstone that only went off every so often, and when you cc'd somewone has plenty of uses and constitutes a large power budget of tree, as capstones do. But it was in no way enough to deal with ranged toplaners just bullying the crap out of melee and making the entire experience horrible because their dmg runes are always on.