This is what will kill 3rd party sellers, companies like gamestop and game selling on Amazon especially when sony and microsoft implement this into their future physical releases.
Game cartridges no longer have the game on them, they have a code you use to obtain the game digitally. Now when you buy a game off somewhere like ebay, or a used game off gamestop, nintendo will say this game key was already used, and tell you to buy the game on the eshop to play the game. Actual physical games are no more, they're being replaced with digital download codes. You will own nothing and be happy