Aluminum and steel CAN be reloaded. Even if the spring back isn't the same as brass, they can be reformed to the correct dimensions with dies. However from a practical stand point, it's not worth the effort. As mentioned, the aluminum cases use Berdan primers, as do many steel cases. That alone makes reloading very difficult. Both will also work harden quickly and split. Also, steel cases would be harder on your dies (even carbide dies) for obvious reasons.