They were meant to be told around a campfire, by people who could not read or write. The repetition was a mnemonic helper, a storytelling device to impress character traits (e.g. instead of saying "Batman" you say "Batman, the Dark Knight"), and a way to take time to think about the next step in the tale (in a way similar to rappers reaching for certain words over and over, as "crutches", because they know they are easy to rhyme).