In the old days, the first task of a young monk was mastering the Psalms. This meant memorization of all 150 Psalms.
If that sounds like a daunting task, it is nothing compared to what it would be like in our day. Which of the liturgical translations would be memorized?
Even worse would be any attempt to memorize hymns, the best of which have been altered by so many hands of varying capabilities that sometimes there is very little of the original left.
The memory is one of the greatest helps to the understanding. When faced with a theological question, it helps so much to bring various previously considered data to bear on the current issue. But the shifting sands of wordings and translations actively stifle memorization.
Theological helps like Scripture, hymnody, and antiphons are rarely store-able in the memory because they are inconsistently presented.