Pastors need to know the flock to preach effectively. Here is a comment from the Westminster Directory of Public Worship. Bold is mine. The pastor

Needs not always to prosecute every doctrine which lies in his text, so is he wisely to make choice of such uses as, by his residence and conversing with the flock, he finds most needful and seasonable; and among these, such as may draw their souls to Christ the fountain of light, holiness, and comfort.

A man who knows his sheep will be able to bring the Word of God to them each Lord’s Day in such a way as to rebuke their sins where they are falling, encourage perseverance where they are growing in holiness, comfort them in the midst of pain and difficulties, and most of all draw them to Christ.

I know it is not possible in every church for the pastor to know every member. But the pastor should be among the people enough to know them well enough to bring the Word to them effectively each Sunday. If he doesn’t know his sheep he might be preaching on Sundays, but he won’t be preaching to them.