For example ...
If I apply a bunch of develop settings on import, after doing later edits, I may wish to see the photo without the template changes but with the later work on it that I've done.
To be more concrete, I often use "Auto Tone" to get a feel for the photo, then start adjusting but the catch is that undoing what the "Auto Tone" does isn't trivial, I'd prefer to just remove it ... why do I want to remove the "Auto Tone"? Because I don't know exactly what it's done...
In other situations, sometimes I'll forget to add "Lens Adjustment" until late and then decide that I want to remove a colour adjustment that I applied before the "Lens Adjustment" (or similar.) I want to keep the profile or manual lens adjustment but just remove the saturation/hue change that I made early on. In this case, doing the inverse of the earlier adjustment works but it clutters up the "develop history" (or steps.)