I think @Fake4000@lemmy.world made a solid point here.
Nintendo goes after those that make money. That includes ROM sites too. For example, Nintendo didn't sue Dolphin developers, they told Valve to take down their software. Please correct me if I am wrong.
I am not saying that Nintendo goes only after those that make money but maybe a money papertrail takes away the anonymousness of the internet. Bank accounts makes finding people a whole lot easier.