They're much more likely to spend time on the easy wins than on anything that'll take time and money to fight in court. Since these folks aren't redistributing any of Nintendo's copyrighted content, it's not as simple of a takedown as an emulator that includes private keys.
Github isn't taking Nintendo to court over one of their users projects. They just comply with the takedown request and remove it. The user/dev isn't going to fight Nintendo to bring it back either.