For one thing, in the case of Reddit, there are sites which exist to archive deleted posts and comments. I believe I've used https://www.removeddit.com/ https:

For one thing, in the case of Reddit, there are sites which exist to archive deleted posts and comments. I believe I've used https://www.removeddit.com/ https://www.removeddit.com/ in the past to read some deleted content. I would imagine it's relatively affordable and easy for someone to scrape social media and store it all, forever.