Perhaps the "single file" feature is no longer very high on the wish-list of the average user, especially since people now tend to share stuff online rather than via physical media like in the old days; this could explain why there is no widely used library to support this use-case.
The single file aspect isn't really a feature for the end-user, the end user just gets content they like. The single file aspect is more about the workflow for the content creator , content aggregators like flash portals, and the ecosystem that affords. Flash portals are all but dead now, but that's another story for another time.
