I attended an excellent sermon today on the meaning of the Garden of Eden myth. The minister, Peter Godfrey, talked about how the serpent is actually a symbol of wisdom, and the act of eating the fruit was an expansion of consciousness.
I was discussing this with someone on the phone just now, and they asked, since the story isn't literally true, why not just jettison it completely? Why bother reinterpreting it?
I think the answer to this is because we are taught these stories as children and they have a way of lodging in the psyche / being embedded in the subconscious (nasty infectious memes!) and if we reinterpret them, it helps the psyche to recover from the unpleasant results of them. Just telling yourself they are not true isn't enough - it works for the rational mind but not the irrational subconscious. The subconscious works in terms of stories and myths (that's why they're important) so if you want to re-educate the subconscious, you have to tell it new stories, or new interpretations of the old stories.
If you have been brought up with the idea that "Jesus died for your sins", or some other nasty, pernicious, insidious piece of mythology, and in the past you accepted it as a truth, your rational mind may have quite properly rejected it; you may have had an emotional reaction against it; but on some level, it may still be buried in your psyche, waiting to burst upon your consciousness when you least expect it.
Therefore, you need to tell your subconscious a new version of the story, with greater mythic power and resonance than the first version, and you need to show how and why the story was constructed in the first place, to get it to understand that all shall be well, and all shall be well, and all manner of things shall be well.
Also, these stories are very powerful and speak directly to the subconscious, and they can actually be used as liberating and empowering myths.
Update: Oddly enough, after I had written this, I noticed that Andrew Brown has written on a similar theme.