by ur logic one can do the same for each doc unit, i mean USF has no heavy tank does it need pershing stock ? do ukf need land matrees /sexton stock ? do okw need jli jagdtiger lefh stock ?
do soviet need kv1 isu is2 stock ?
Again there is no heavy tank mechanism in game. There are vehicle with direct fire made up with high armor value with higher cost. So USF do have vehicle with direct fire and they perform appropriately with their low cost. And yes, ukf also need non-doc mobile heavy artillery as well but not land matress since it has different mechanism than what a mobile heavy artillery should have. Anyway, that's gone too far and being off topic, so start another thread if you want to discuss it.