I don't understand why that would be more useful to me than my current storage and backup system.

I already don't store needless duplicates, and when I decide to store something, I don't have to go back to the source after I have stored it. That's the whole point.

How is IPFS helpful?

Has IPFS made anything happen that couldn't have happened without it?

What are its biggest accomplishments, outside of its own spread?