Size. If all the translations are in the same program then it will grow exponentially, and on a mobile device space is precious. Plus, I don't want to download 10000 languages when all I can really understand is English and Korean.

This consideration is far more important IMHO than convenience. Another alternative would be to have the translation files on a server somewhere and have them downloaded on first run.

Not saying any of this should be considered now or in the near future though...