Nintendo's reputation of bc? Since when???
Nintendo consoles only started becoming bc last gen, and only because the architecture between the GC and the Wii was so similar, which continued on with the Wii / Wii U because the consoles literally utilize the same motion sensing technology and controllers! Same thing with handhelds... the GBA was made to handle original GB games, and the DS had an auxilary slot in earlier models to handle GBA games.
Looks like you just answered your own question.