This is clearly a niche tool. If you want to efficiently modify the profile of a neck, you will need this. It will allow you to make templates from a model neck, remove the guesswork, and enable a proper comparison between 2 neck profiles. Also, it is extremely useful during the reshaping job as you can monitor your progress using the templates you made before starting to remove wood.
Quick tip, use masking tape on the neck, the needles of the tool are metal and could easily scratch the finish.