I have zero proof for this theory, but I have a sneaking suspicion that the reason Nintendo designed the DS the way that it did was to curb emulators. In the company’s mind, having to emulate both screens, the touchscreen, the microphone, and even some unique in-game mechanics that happen when you close the clamshell case (like that one puzzle in Zelda) would make it really difficult. And I can imagine that emulator developers did struggle trying to get everything locked down.