Christ's church needs authority. While more and more people today believe in personal revelation from God, more and more are rejecting the idea that any one person speaks God's words with authority--as if from His own mouth.
God has reaffirmed the need for a bona fide prophet as an authority of truth. Organized followers of Christ have more power to battle the adversary and to endure the calamities of the world, because of their unity. To deny the authority of any revelation intended for an entire group is to suggest that God has no need for group-wide revelations, or that if He does, He will tell each person in the group individually and they will all come together of their own accord.
Heavenly Father reveals His will for His children through His prophets. He always has, and He's never retracted His promise to do so.