First we listen to God, then we cry out to Him in faith on the basis of His promises. Learning the catechism by heart is probably a better expression than memorization. Memorized things are often forgotten. Repetition is not a lot of useless babbling. Short sections from the catechism, prayed and pondered daily, are a boundless source of comfort and strength for living the Christian life.
Repetition is good.
Vain repetition is bad. The repetition of texts which are anchored in the Word of God enables that Word to penetrate deeply into our subconscious minds and to the very depths of our souls. The Holy Spirit continues to minister to us, even when we are unaware of it, through the Word of God which is learned by heart and repeated in prayer. On the Journey Luther's desire was that the catechism be viewed as a companion on a lifelong journey. By praying the catechism, we learn to listen to the Word of God in those things which have been learned by heart.