The simplest answer is often the correct one.

Just for people to see who kills NMs. Not necessarily the most recent or most often over time. Use it for bragging, etc

While unintentional, it will also provide, eventually, a list of all implemented NMs (as only implemented ones can be killed). This assumes nas has all NMs as possible to show up on the board.

...TopShelf told Nas to roll back all your ZNM gear, do the gilpocalypse and nerf Fishing/RNG into the ground.