I believe the reason why they do not perform real time translations is because they want to be 100% sure that whatever is said and translated means the same thing in both languages. This is done to prevent misunderstandings and misconceptions from being formed based upon the translators work. If they say it, its official but if a fan translates it, its unofficial and they do not have to worry about it as much because they could say something got lost in translation if they did not like the translation.