Because why would they? They would have to dedicate a shitload of resources to optimizing decades of work for PC so a small slice of the market can buy old stuff. All of those games would stop being a hacky thing you're okay with bugs on to a thing Nintendo now needs to support. Not only software, but widely varying hardware and worse yet, controllers. There's simply no way they release wii games as paid products on PC and make a satisfying experience with a keyboard/mouse.
I have seen this idea now suggested multiple times. Nintendo's business model is sound. Protect the "official" experience at any cost so that it's 100% clear when you're playing on a Nintendo console vs a non-official emulator. Blocking dolphin's steam release is consistent with this goal; if it's on steam, it looks like a real product and non-tech people might start to think it's official.
Emulating old systems on new systems is something Nintendo successfully did in the past, monetizing unmonetizable.
> so a small slice of the market can buy old stuff
You might be underestimating the size of this slice. Nintendo is fundamentally a toy company, just like say Lego, and they rely on pretty much the same process: indoctrinating kids into using their products, then waiting until they grow up so they help indoctrinate their own kids. The control over this process might be more important than the sales figures.
They already lost several generations of kids in Latin America and former USSR precisely because they failed to control the pirated clones market there. (either ignoring these markets or being too heavy handed in them; it's a long story). The piracy is happening with or without them.
However, as a toy company, they are focused on physical products more than software, so they probably aren't ready for the emulation on the hardware not designed by them.
I think you're underestimating the effort required to complete the task you're suggesting, probably by multiple orders of magnitude.
The point that people seem to not get is that Nintendo's entire brand rides almost entirely on having a "perfect" experience. Word is that they spent an extra year just on polish for TOTK; having played it myself, I believe it. No game is this quality on release on any other platform. They have their walled garden in the switch (and previous consoles) where they make sure it works absolutely perfectly, and it costs them a lot just to do that. I believe it might be literally impossible for any company to achieve that reputation under any other circumstance, and the polar opposite circumstance is emulating your game on the hyper-chaotic hardware situation that is PC gaming. Not to mention the fact that modern emulators almost universally offer things that Nintendo wouldn't dare: upscaled textures, higher FPS (this is a huge one that causes a litany of bugs), mods, etc. Even a release to PC wouldn't matter because people would demand parity with what emulators offer or just go back to them.
What you are suggesting would require the following for every one of them:
1. Thorough testing for performance and stability to ensure a PC port works at all
2. Thorough testing of innumerable hardware configurations
3. Thorough testing of every conceivable type of controller, display, keyboard/mouse, etc.
4. Ongoing support of some sort, forever.
Nintendo's focus on quality means that what you're asking is probably a multi-trillion dollar effort that would take decades even if they increased their staffing by 10x. Do you think there's that kind of money in it for them? To top it off, I will repeat that hardware on PCs is far, far more chaotic and unpredictable than any other platform. To even attempt this would be folly; it would be guaranteed to be a buggy mess (like how emulators all have been and to some extent remain), and their main selling point would be ruined.
It seems self-evident to me that Nintendo doesn't really care about emulators for old games. They throw their weight around and make broad gestures to say they hate it, but that's the point. They know they can't stop people from doing this stuff, and they make almost no effort software-wise to prevent it. They just want people to know without any shred of doubt that if they play a nintendo game outside of a platform they have deemed worthy, they are not getting the "real" experience. This absolves them of any blame when the games inevitably don't work right, and it makes clear that they will never allow emulators to become "official" platforms. I'm sure they carefully weigh their actions to ensure they don't actually extinguish emulators, and I wouldn't be surprised if they have covertly contributed to their development at some point. These old games are unlikely to be money makers, but keeping people playing Nintendo IP will make them more interested in buying more in the future.
I think Nintendo has a similar attitude to Apple in this regard. Sure, Apple could probably make a lot of money by selling subscriptions to iMessage on non-Apple platforms, but that sacrifices control and gives people a reason not to buy their hardware.
Nintendo has historically demonstrated that both of those things are extremely important to them. For example, it's not uncommon for Sony and Microsoft to sell boxes at a loss for the first few years, making their money back in software. Nintendo typically doesn't do this.
The other thing the companies have in common are massive fanbases who will buy anything they release and defend every move they make. Both their fans have the ability to spin negative news into positive news to keep up the fantasy that the company loves them and is looking out for their fans' best interests.
I would definitely buy a lot of Nintendo games if they were available on desktop. But they would much rather push their consoles and resell you each game each generation.
If Nintendo had a ROM store where I could buy game ROMs and play them on whatever system I wanted to, I would spend a lot of money.
In fact, Nintendo more or less did this with the Wii U, which was a commercial failure. I bought an incredible amount of games from the virtual console and oftentimes on sale for a few dollars. Then with a modded Wii U, you can extract the ROMs. Now I am playing GBA games on an actual GBA (with an upgraded screen extracted from a DSi) and SNES games on a MiSTer FPGA connected to a PVM with an original SNES controller. Ever since they shut down the Wii U online shop, there’s been no new legal way to acquire these ROMs. What a bummer and too bad the market didn’t appreciate the Wii U for what it was: the ultimate collection of past Nintendo games.
Oprn their own PC based game store
Sell only Nintendo first party games in it
Require a Nintendo online account
They would defeat whatever is bothering them and make a lot of money
But they won’t do this