NES controllers especially are great for kids, for whom even SNES controllers are confusing with their four face buttons plus two shoulders—and I remember, as an NES kid who didn't get another console until I bought myself a PS2 in college, finding anything with more buttons than a 3-button Sega Genesis controller kinda tricky at first, though I eventually managed well enough to hold my own on some N64 games at friends' houses. Only "complicated" controller I've found to be almost as usable for my young kids is the Gamecube controller, so they got that right after all I guess.
Sure you can get knock-offs, but Nintendo doesn't screw around with controller quality, even on cheapish emulator systems.
[EDIT] also I've owned two Wii-connector-to-USB adapters, both from Mayflash, and both were janky and soon stopped working at all, so just buying the controllers (or just using the Wii Classic Pro controller, which is what I actually attempted those times) hasn't given me acceptable reliability.
For a reason that might make sense, but which I rarely see repeated: standardized “first-party” products allow a level playing field for speedruns and the like. Whereas nobody’s gonna trust a run you did on your modded toaster.
A more likely reason, though, is that quite frequently now collectors are also content-creators (gamer YouTubers, etc.) and these folks need officially sanctioned games and consoles for the same reason professional artists need official copies of Photoshop: you’re way more likely to get sued as a business profiting off of piracy than as an individual just playing.
Then there's Christmas. My partner happily bought me a Nes Mini for Christmas, I don't think she would have been so happy to get me a raspi, controllers, case, possibly install emulators, roms, etc.
Its like building your own PC, most people on HN could probably do that no problems, the majority of the population would prefer to get a Dell.
I could see the appeal of them maybe designing the VCS as a SteamOS box in a cool woodgrain retro-styled case, even I'd be tempted. Stick an officially-endorsed emulator and ROMs on there and you're well away. But this talk of their own proprietary gaming platform? What developer in their right mind would want to develop games for such a small market?
If they'd actually positioned it as a low cost SteamOS box which can run a decent amount of PC games for cheaper than most PCs, they might have at least have a niche market for it. If they some integration with SteamOS to launch an Atari emulator and they'd have some extra selling point. But it's basically just a small low-powered Linux PC that might get a few exclusive deals.