Once again, people are surprised that the largest multimedia franchise on earth, known for its lack of quality in all regards except merchandise, is cutting corners and saving pennies as often as possible in order to secure its profits.
You get rich by NOT spending money, dipshits. You figure out how to game the system to achieve maximum profit for minimum investment. And because Pokopia is a Switch 2 hardware game, the most expensive spinoff thus far, they HAVE to shave a few bucks/yen/whatever the dicks off of investments in order to have a promising profits return, and that includes cheaping out on real cartridges entirely.
ESPECIALLY because a cut of those profits are going towards Koei Tecmo, diluting the distribution chain that's already an inherent four-way between GameFreak, Nintendo, Creatures and TPC (TPC handles marketing, so naturally they get a share even if they aren't actually involved with development).