The problem with distributed storage is they place too high of a requirement on edge nodes, which people have to host, and they synchronize too slowly for real time messenging. If I upload a 1GB video to my server's chat, that storage load should not be replicated on many other nodes. Who pays for that disk space? The federated model is a lot more robust in this regard.

As far as archiving is concerned, many archiving orgs will pop up if their discussion servers and public facing websites can't be traced or easily shutdown. The protocol itself can't archive things, but it protects the people doing the archiving work and gives a place for websites like Annas Archive to live without relying on IP and DNS. The idea is to amass enough uncensorable social power so that such efforts can't be banned or shutdown, then you can use existing protocols like BitTorrent all you want.