Personally, because I put my time into making something for the community for people to use for their own personal use and these sellers ignore my wishes and turn around and sell my work and make money off it. They aren't paying me to use what I made. And they aren't paying Nintendo to use what they made. They are stealing things and making money off that stolen work.
If someone stole something from you would you be ok with that?
Let's say you are a sculptor. You spend weeks making an awesome sculpture of Zelda because you like the game so much and you donate that statue to your local library so that everyone can see it. And now imagine someone steals that statue and sells it on eBay for 1 million dollars and the cops don't arrest the seller or even stop the sale. They just let the thief get away with it. Would you not be upset? Or would you be fine with people taking your stuff and getting rich off of your work because you're not a weirdo?