I had some "real" electrical work done this summer on main feeds to the house. I got to talking to the electrician and we hit on GFI outlets and stuff. His comment was that the GFIs now required are a safetry redundancy. He said more and more codes are adding a failsafe or back up system to the protection and GFIs are just that. It is a second layer of protection.
Placing a fuse at the track is like that I think. It is adding second layer of protection in case the first fails.