[ralfd]

I think this is simply survivors bias for every information transmitted orally. It had to be repetitive, or people couldnt remember it. See here for the Ilyad:

http://faculty.gvsu.edu/websterm/Read_Iliad.htm

> For an oral poet, however, such repetition is not a fault, but a vital technique (Lord 3–67). Repetition is a psychological necessity in oral discourse, which vanishes as soon as it is uttered

[ino]

It's also useful when the text makes no sense, is offensive, outdated and/or just plain wrong, so with repetition they can always say "that's how we always did it so it's right" to shun off the people who grow up, think for themselves and start questioning the texts.