Why is everything Catholic done in latin?

In the first place, "everything Catholic" is no longer done in Latin. More churches today celebrate Mass in the vernacular than in Latin. In the second place, Latin as a language goes back many centuries B. C. and was the official language of the Roman Empire at the time of Christ. Despite recurring persecutions, there were many Christians in Rome almost from the beginning. Worship was most likely conducted in the local language at first, and as Latin itself broke down into the Romance languages after the fall of Rome (A. D. 476). the "old language" probably persisted because of custom and tradition. It may have taken a while for clergy to realize that no one in their congregations understood the language of the Mass any more, and by then the custom of worshiping in Latin must have been firmly entrenched. Meanwhile, however, in the Eastern Roman Empire (which became known as the Byzantine Empire after the fall of Rome), worship was conducted in Greek or, as Christianity spread, in the local languages. (Look up Old Church Slavonic.) In the West, Latin continued to be the language of scholarship and of international communication for many centuries after it had ceased to be anyone's mother tongue, and this fact is no doubt related to its continued use in worship. Then at the Reformation, when reformers whose protests against certain Catholic practices ended up founding new denominations, the use of the vernacular in the services of those churches most likely strengthened the determination of the Church of Rome to stick to Latin.

Latin was spoken ALL OVER the Roman Empire.

Early on, it became obvious to the Church that evangelizing the Empire was in the Church's interest. Therefore, it decreed to offer all Masses in the Latin language.

Use of the Latin language in the Mass continued as a custom long after the Roman Empire collapsed and the language died.

Well, since Vatican II now the mass is done in the local language.

Mass was in Latin because the Roman Empire became a Christian Empire, and the main language of the Roman Empire was Latin. Since Latin was the official language, and Christianity was the official religion, church was done in Latin. It stayed that way until the Councils of Vatican II. The church was reluctant to change it from Latin since it had been part of their tradition for over a thousand years.

It isn't anymore. Latin was at one time the common language of the Roman Empire and Latin was adopted by the Church. As languages changed the Church was reluctant to change the Latin form of worship.

>>Originally the mass was only in latin.<<

No, the Eastern rites of the Catholic Church have always used other languages. Liturgies in Latin developed in the Latin rites when Latin became the common language in the West.

Since Vatican II, everything is done in the local language of the faithful, but Latin still is there. The church was HQ'd in Rome and remains so today.

Because it is a fun language =D

Because it was the language of the pagan Romans, and Christianity is basically a plagiarization of earlier pagan myths.

They use Latin because it acts as an aphrodisiac on altar boys.