The Gospel does need to be preached in every language. That was one of the gifts of the Holy Spirit to the infant Church. However, the early Christians realized pretty early on that in order to preserve doctrinal and theological teachings, particularly concerning proper worship, it is good to use languages that are "dead," such as Greek, Latin, classical Arabic, Aramaic, and Old Slavonic.
you're right, the Gospel doesn't NEED anything. It's the people who need to understand, as God showed in the new testament. Is this a difficult concept or do you often speak to others who speak a languiage you don't understand?