I think preservation is happening, the issue lies in accessibility. Projects like Archive.org are the public ones, but it is certain that private organizations are doing the same, just not making it public.

This is also something that is my biggest worry about the Fediverse. It has tools to deal with it, but they are self-contained. No search engine is crawling the Fediverse as far as I've looked, and no initiative to archive, index and overall make the content of the Fediverse accessible is currently in place, and that's a big risk. I'm sure we will soon be seeing loss of information for this reason, if not already happened.