Oh, that's absolutely a big part of it. There was no "reading public". Very few people could read and write. I assume all the repetition has to do with making the stories better-suited to memorization and oral retelling. I don't mean any of that as some kind of put-down of the ancients, it's just a fact that a modern reader is going to find the material difficult, and, even once acclimated to the difficulty, of limited appeal, with few exceptions (and I'd call out Gilgamesh as the #1 exception)