I forget where I ran across it (Disputations, maybe?) but someone was complaining about the "vain repetition" of prayers in the Rosary. Well, hopefully the repetition is not being done in vain, but instead quite purposefully. Repeating prayers is of course a good way to focus and calm your mind for meditation upon the Mysteries of the Rosary (incidents in the life of Jesus, and that of Mary, which are all pretty much her cooperation with things Jesus/God was doing). Beyond that, however, repeating a prayer causes you to focus again and again on the prayer itself and what it really means.
Frex, you might be praying the Our Father. One time, you might say, "Our Father...." and find yourself thinking about how your own father's love points to the infinitely greater love of God for His creations and adopted children. Another go-round, you might say "give us this day our daily bread" and start thinking about how you really do depend on God for everything, or His faithfulness in continuing to do so. "Deliver us from evil" is always an attention-grabber.
Praying ten Hail Marys at a time gives you time to think about the event associated with the decade and its implications, but the words of the Hail Mary have you returning again and again to the basic mystery of the Incarnation, the communion of the saints, and "now and at the hour of our death".
Then, at the end of every decade, you come out to the Glory Be -- into glory beyond time and space and the eternal contemplation of the Trinity.
In effect (Maureen realizes after a lifetime, being rather slow), the Rosary tells again and again the story of the creation of the world, Jesus' life and the Christian life, and life forever in Heaven with God. Just as reading the Bible again and again does. Sorta like the Mass does (though that's got actual sacramental things operating, and the Rosary doesn't). Hmmmmmmmm.