>>713115361A huge percentage of gamers (not me mind you) resell games / trade them in for credit for new games extremely often, I think its less common now than it was in the past but even 10 years ago there would always, every single time I was in a gamestop, be multiple people lined up to trade in their old games for new ones.
Normies do not give a shit about replaying old classics once they've beaten the game its done, time to get a new one.
To answer OP's question its literally just to appease third parties who dont wanna play for expensive cartridges but want physical store presence, its on them to not use it, not Nintendo for giving an option.
Of course the only reason any sane person would buy a Nintendo System is for it's exclusives, and the exclusives will most definitely all be real physical games, since the kinds of publishers who opt to use game key cards never cared about their port in the first place and just want to make a quick cheap buck off the new console release.
Mind you I'm retarded for still being a physicalfag when we have data to show that the physical version of a switch 2 game is literally the worst version you could own in terms of load times.