Physical media has the inherent benefit of being difficult to remove from the customer. Because of the several thousand years of precedent and “argument” has lead to the current protections many countries have.
Digital distribution of Digital goods has significant benefits to the customer and producer over physical distribution. A lot of physical game media at this point is basically a license key and a mostly working game that needs downloaded patches they were still developing while the discs were being printed. The downsides are the current legal mechanisms and that a lot of people involved in the producing would like to continue to eat and pay rent.
Don’t act like this guy.
I would be surprised if a cartridge being discontinued would kill an open source project like this. They could switch to a different cartridge.
I’d assume they’re doing the one for now because it’s cheap-ish and has widespread availability. There’s little reason not to expand to other cartridges once the rest of the printer is more stable.