One area that I’m familiar with, lost films and film preservation, is not done by Redditors. I’ve met some of this country’s top archivists and even toured one of the country’s biggest vaults. This is work done by a handful of highly trained professionals. Many can do half assed jobs, but doing it right requires serious training in film history, archival techniques, and other topics in art.
Basically, Reddit contributes nothing to film preservation.