.3ds files were only used on the flashcarts
They are also now used in emulators like
Citra, but regardless it doesn't answer the question.
, sky3ds+ is a waste both of time and money. and gateway / stargate are useless shits as the so called devs of the flashcards have proven.
Irrelevant. Although I don't consider installed games to be viable long term for any console regardless of the practices of a given group.
Those are the only 3 cards that used .3ds file formats for the console. So its .cia files to install and play. the .3dsx files are homebrew files which retail games cannot make use of.
Again, it doesn't answer the question. Just because no one bothered to create a CFW that can run cart images as mounted files doesn't in of itself answer why that is the case. That's circular reasoning.
CFW can now mount Gateway emuNAND and update to the latest firmware, but cannot load .3DS files. Why? I get that, physically, the flash cart has a space for a microSD card to go, but with Homebrew working I don't see why it has to be located on the cart in order to mount. Even if that is the reason a CFW should be able to make use of such a slot on any number of carts openly.
EDIT: I found an interesting thread
here describing an alternative solution:
made a protocol to access the raw SD sectors in the SD card inserted into the Gateway red card and Supercard DSTWO + which would allow for really anything you can think of involving file transfers if you program it into a homebrew.
As far as the Gateway, this doesn't mean too much other than having an extra microSD card slot (which is pretty big in of itself, though I find the next part much more exciting). If used for the SCDS2+, however, you could basically set up a DS/GBA save editor accessing the .sav files from the NDS games you play on the flash card, and the GBA emulators you play on it - which is something I want to look into building myself for a full fledged Pokémon Homebrew Bank that encompasses every generation, 1-7.
https://github.com/shinyquagsire23/gwcard
Which means that the SD card inserted into a Gateway cart can be accessed by CFW rather easily, which wouldn't just be of use for backup game loading, but as an alternative place to run homebrew from. That doesn't in and of itself allow for 3DS files to run, but it means that if the problem is access to the Flashcart, well, it's not a problem, so I'd like to understand what the problem is if any.