Adam Clarke on Psalms 78:4

We will not hide them - In those ancient times there was very little reading, because books were exceedingly scarce; tradition was therefore the only, or nearly the only, means of preserving the memory of past events. They were handed down from father to son by parables or pithy sayings and by chronological poems. This very Psalm is of this kind, and must have been very useful to the Israelites, as giving instructions concerning their ancient history, and recounting the wonderful deeds of the Almighty in their behalf.