Why does the church exist? Even if we can give the theologically correct question, what does it look like practically? The church exists, not for itself, but for mission—to carry out the mission that Jesus Christ gave to it. That mission is to embrace a biblical commitment to planting healthy, reproducing churches.
making known to us the mystery of his will, according to his purpose, which he set forth in Christ as a plan for the fullness of time, to unite all things in him, things in heaven and things on earth. — Ephesians 1:9-10 (ESV)