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

Questions & Answers
1

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

2

Scene 1 (code the same for three scenes)
Main Camera
Directional Light
Canvas (no prefab)
Panel (no prefab)
Text
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