Why does Camera.Render only work when rendering to RenderTextures

I'm not sure whether this is intentional or if I'm doing something wrong on my end but I can't seem to manually render to the game view. My scene consists of two cubes and a camera. I have this script attached to the camera;

 public class CameraRenderTest : MonoBehaviour {

 public GameObject ObjectA;
 public GameObject ObjectB;
 
 // Update is called once per frame
 void Update () {
     ObjectA.layer = 0;
     ObjectB.layer = 9;
     camera.Render();
     ObjectA.layer = 9;
     ObjectB.layer = 0;
     camera.Render();
 }

}

The Camera component is disabled to avoid automated rendering. I have the culling mask set to the default layer and the clear flag set to solid color. When I apply a RenderTexture to the camera both cubes are rendered to that texture along with the background. However if I leave the render texture field empty the game view stays blank. Again I'm not sure if this is a flaw with Unity or it was never intended handle what I'm attempting to do.