Reasons for adding a camera to a scene in Three.js?

Why should I add a camera to a scene, although I am already passing it to my render method? Every example I have seen in the repository adds the camera to the scene, e.g. weggl_geometries. But after removing scene.add( camera ) it still works...

init function

camera = new THREE.PerspectiveCamera( 45, window.innerWidth / window.innerHeight, 1, 2000 );
camera.position.y = 400;
scene.add( camera );

render function

renderer.render( scene, camera );