Earlier quoted context omitted.
If I get it right, the idea is that if you want to make sure it's there one year later, you set up your own server and host the files on your own. IPFS just allows others to distribute a mirror of the files.
Why would nodes in the IPFS network voluntarily act as a load balancer for my VPS? Usually I have to pay for load balancing, so I'm a bit suspicious when someone claims I can get it for free from IPFS.
Why would nodes in the BitTorrent network voluntarily act as a load balancer for your movies?
Same reason. Maybe you and I cannot explain the reason, but that does not mean that it doesn't happen. People don't always act in a 100% rational, for-profit manner, no matter what economics textbooks tell you.
(Edit: Of course the likelihood of your content being mirrored rises with the quality of your content.)