Who are we?
We are digital librarians. Among us are represented the various reasons to keep data -- legal requirements, competitive requirements, uncertainty of permanence of cloud services, distaste for transmitting your data externally (e.g. government or corporate espionage), cultural and familial archivists, internet collapse preppers, and people who do it themselves so they're sure it's done right. Everyone has their reasons for curating the data they have decided to keep (either forever or For A Damn Long Time). Along the way we have sought out like-minded individuals to exchange strategies, war stories, and cautionary tales of failures.
We are one. We are legion. And we're trying really hard not to forget.
-- 5-4-3-2-1-bang from this thread
I think for me, it's because it's sort-of (though not!) self-archiving.
If a site has a reasonable amount of popularity and subscriptions, it would take that site going down, plus all the sites that communicated with it, for the data to be fully lost.
Not to mention that a lot of the sites are run by reasonably altruistic people, who are more likely to hand over than just shutter.
A fair point!