Legit I speculate sometimes companies like Nintendo feel threatened by their own backlog.
Like, I legit do sometimes wonder if it's because they're scared people will like the old games too much that they won't buy new ones and that they'll harm sales.
Which is silly thinking and only shows a lack of confidence in your own project, but hey, I got no idea as to any better reason why companies act like making emulators is some Herculean feat when we've had people in their basements making near flawless emulation on their own dime for 2 decades now.
I think that simplifies things a bit much. It probably comes down to profit margins and wanting to keep the value of the IPs high. There is definitely the argument of getting one's fix through an older title but one could also assume there is probably more money to be made on newer releases, especially low budget re-releases they'll try and sell at full price, than putting the effort into researching and re-releasing games people automatically (and honestly rightfully) expect to be discounted.
NES/SNES are probably one and done now when it comes to emulation, they've been built upon and upon for over 20 years now, but public interest has arguably been waning. It wouldn't surprise me if they're undervaluing them now and seeing more money long term through the subscription service. Why they took down FE1 after only ~4 months though is beyond me and one of the dumbest things they've done IMO.
N64 is probably a mix of imperfect emulation and valuing the games more highly. On top of being a more multi-player based system and the weird controller, this system is in it's own weird nexus.
GC and beyond is probably valuing too highly or seeing chances to re-release at low budget but full price. Have heard of some potential issues regarding certain Wii games and motion control as well that would require extra effort. Ex. Metroid Prime 3
They'll harass YT channels and Twitch streamers who try to bring attention to it and try to flex some lawyer muscle on a ROM site or two at worst and that's about it.
Emulators themselves are 100% legal. Nintendo, by all accounts, can't stop a thing, and I'm dang thankful for that. Soooooo much art within the industry would be lost if they had their way.
Definitely think at this point it's more so a pandora's box situation lawyers are making them avoid than anything else at this point. IDK maybe it's me, but I think at this point with the industry as old as it is I don't think emulation is as much of a threat to profit as it once was or is seen as a given now and that companies just have to keep up appearances on in most cases.
To their credit, if there is one thing the Giga Leak has shown is that Nintendo is amazing when it comes to preserving things internally. They just don't want to share or make things public. It wouldn't surprise me if the Giga Leak would contain proof of concept stuff for the original Metroid Dread. lol