As far as I know, the Catholic Church considers God's revealed truth in Sacred Scripture to be part of, but by no means the sum total of Divine Revelation. Sacred Scripture is the written part of our Traditions, but it is entirely possible to have a Catholic Church without Biblical literacy (or literacy at all).
So, why did the Church decide on having a canon of scripture in the first place? Did the Church Fathers (Augustine and prior) consider that having a set of writings that resides somehow outside the authority of the Church would eventually cause fractures due to private interpretation? Or was it necessary to prevent further errors owing confusion coming from the existence of the many gnostic and apocryphal later writings?