When you get a good deal on a blade you like in the color you dont.
Or if you have used the knife enough that the finish is wore off and showing the metal of blade in large sections.
Or you want to modify the blade
Or because some coatings are so thick you get stuck in wood easier.
I've stripped one because the coating was flaking off. I didn't want rust developing under flaking coating. I currently have many users with coating wear but no flaking yet. I'll eventually strip them as needed.