Does directLight only work when it is a child of a Scene?

I want to that sub-directLight has same position and rotation with camera always.
This is because, if there is only a world light source, it may be difficult to identify a place where the light does not reach.
If DirectLight was a child of camera, it didn’t work.
Does DirectLight only work if it is a child of a Scene?
test_skeletone.html (3.7 KB)

// scene.add(directionalLight);

Add camera to scene to activate the camera light.

thank you, for your reply