It would be a big, expensive case, and as there are well-funded organisations that rely on the precedent not being set against them in both directions, both sides would get interested third parties funding their legal fees. No one wants that, so Nintendo stick to claiming emulators are illegal on their website

I would assume particularly that no one who has big interests there wants it to go to court because once there’s a ruling and a precedent is set it becomes much harder to change if you’re on the losing side. So, for example, if game publishers lost and it was clearly ruled legal that consumers have a right to make software work with hardware that the software was never intended for, that would make it much harder for publishers to fight emulators without some additional problem like trademark infringement. The advice I’ve heard is unless you can be absolutely certain how a judge will rule, you want to avoid going to court because strange and unexpected things can happen in a courtroom that can be very bad for you.