This may help to create a better intuition of SSB decentralization: every time you say "SSB should", or "Patchwork should", try replacing that with "All the people in the planet should" and realize how nearly impossible it is to achieve that. Because...

But that doesn't mean, e.g., that everyone on snapchat will be recording everything.

That's because there is just one Snapchat app which the Snap company controls. With SSB, every time someone makes an app or program, anyone can fork that and make a version with search engine crawlability and storage forever.