The answer might be the legality of using copyright to block functionalities, the link describes how Accolade challenged SEGA on those grounds a few years later

The answer might be the legality of using copyright to block functionalities, the link describes how Accolade challenged SEGA on those grounds a few years later and succeeded: "The legality of this system was challenged in the United States by Accolade in the court case SEGA vs. Accolade, which ruled in Accolade's favor. The verdict set a precedent that copyrights do not extend to non-expressive content in software that is required by another system to be present in order for that system to run the software." In case of Nintendo, it sounds like a unlicensed cartridge still had a choice to work on the Gameboy and NOT infringe the Nintendo trademark. But if it decided to show the Nintendo logo on bootup, it explicitly infringed on copyright...