Two Reasons.

First, Latin is still very much alive in languages today. More than half of English words come from Latin, and studying Latin gives an excellent foundation not only for expansive English vocabulary, but also for learning the many Latin-based foreign languages being spoken around the world today, such as Spanish, French, and Italian.

Second, studying a foreign language gives students the tools of verbal expression in their own language. Students learn English grammar more effectively by rigorously studying Latin; that is, they learn the reasons for, and the uses of, the parts of speech learned in their English classes.

For a closer look at the Latin texts we use, see Lingua Latina and Wheelock's Latin.