A lot of what enables this is centralized infrastructure. If you have your messages and browsing history and files on your own device, and you make end-to-end encrypted connections to the people you talk to, it's a lot harder to do this kind of thing. Because you have your own personal copy of the thing from when it first happened and if you remember it you can go back and verify it yourself. Then you can point that out, and anyone else can go into their own copy from however long ago and see that the fake doesn't match the original.

Social media companies notoriously blocked users from sending a story to each other in DMs a couple of years ago. It's not a stretch to go from there to deleting past messages in order to memory hole something. And the companies may not even be doing it by choice if they're being pressured by a government.

They can't do that if your data is yours and they can't read it, instead of the only copy being on their servers.