Ease of access in all cases. The wii has internal memory, and easily accessed (on a pc) external memory as well as exploits. The GameCube has only has memory cards you can’t plug into a pc, there are ways around it but you have to spend money. So wii just needs an sd card and specific game.
GBA game’s at this point have better tools, no one ever made great tools for ds modding, so less user friendly tools, less mods.