Earlier quoted context omitted.
Unlike a disc, you can't use the code without going through the PlayStation Store. And you likely cannot resell it, either. You can't buy a non-Sony PlayStation, I guess they'll argue it's similar.
It does seem like a reasonable middle ground would be something like selling a dongle that provides PIV attestation of ownership, that could be resold and could even be used across platforms. Of course, there’s no incentive for the console manufacturers to offer this.
The NES and SNES for example had their famous lockout chips which gave Nintendo a monopoly on releasing games, except for the Activision/EA thing were they reversed engineered the chips.