Why would a tutorial on sene managing use a prefab for some GOs and not others with the same name

In multiple scenes the tutorial used a Prefab for one game object (Scene Manager) but not for a canvas, a button, or a panel even though he used the same object names in all scenes. I would have used Prefabs in all cases. Is there a reason he chose not to do it that way? Thanks: @MarleDavid

Scene 1 (code the same for three scenes)
Main Camera
Directional Light
Canvas (no prefab)
Panel (no prefab)
Button (Load Next Scene) (no prefab)
Event System
Game Manager (the only prefab) Que: It works but Why? I would have used prefabs in all cases