First blockchains are slow. Second you can put things in the DHT without having anything to do with a torrent.
I suppose you could just keep your personal computer up and keep announcing, but then you are really just storing information on your computer and not really storing it in the DHT. Feel free to correct me if I'm wrong.
Basically it makes it a bit easier to layer your special application on top of the mainline DHT, help your peers find each other, and make it a bit easier to publish some metadata about your peers.
That way you can take advantage of millions of nodes in the DHT and not just the ones running your special application.
But if you need stronger guarantees or availability those should come from your application, not the mainline DHT.