How do we really know if we've lost something we didn't care about in the first place?
The vast majority of the silent films that have, apparently, been lost or allowed to decay may be interesting as artifacts or as history, but they were not going to entertain anyone or end up being monetized in any way. Their lack of commercial value is what doomed them. Nobody in Hollywood passes on a buck that can be made from a piece of content.
Apathy is what cost us this material. How do you preserve everything anyway?