Game-key cards are different from regular game cards, because they don’t contain the full game data. Instead, the game-key card is your “key” to downloading the full game to your system via the internet.
Pay a premium for a physical copy of your game, and the cartridge may not contain the actual game. Only on Nintendo Switch 2.
If this is going to be what Switch 2 offers, I’m fully out
Edit: I checked with a friend. Normal game cartridges are still a thing. One thing that makes them slightly better than digital downloads (albeit still imperfect) is that you can at least trade, sell, and buy them used. Not as good as physical media, but slightly better ownership rights than buying a digital copy.