Why does not the ambient light work in this example?

var scene = new THREE.Scene();
var camera = new THREE.PerspectiveCamera(75, window.innerWidth / window.innerHeight, 0.1, 1000);

var renderer = new THREE.WebGLRenderer();
renderer.setSize(window.innerWidth, window.innerHeight);
document.body.appendChild(renderer.domElement);

var geometry = new THREE.BoxGeometry(1, 1, 1);

material = new THREE.MeshStandardMaterial({
  color: 0x0c79bf,
  roughness: 0.71,
  metalness: 1,
  normalScale: new THREE.Vector2(1, -1), // why does the normal map require negation in this case?
  side: THREE.DoubleSide
});


var cube = new THREE.Mesh(geometry, material);
scene.add(cube);

var alight = new THREE.AmbientLight(0x404040);
scene.add(alight);

camera.position.z = 5;

var animate = function() {
  requestAnimationFrame(animate);

  cube.rotation.x += 0.01;
  cube.rotation.y += 0.01;

  renderer.render(scene, camera);
};

animate();

body {
  margin: 0;
}

canvas {
  width: 100%;
  height: 100%
}

<script src="https://cdn.jsdelivr.net/npm/three@0.122.0/build/three.min.js"></script>