Physical to Digital Trade-Ins?

[Goemar]

The only way this would work is where the person has to post the physical version to Nintendo in order to get a code. But that's a lot of work for Nintendo for zero profit. And there's no guarantee the code will be compatible with the next Nintendo console, or even reusable if your current console is stolen etc.

Cross-platform purchases aren't the norm. It's only really Sony that does it. It's not like Nintendo isn't transparent about this, they make it clear that the game you are buying is locked to that system and that's it.