[tptacek]

That's exactly the wrong way to look at it. Everything is potentially a file, but not all cryptosystems have the same use cases. The needs of message encryption (forward and future secrecy, for instance) are not at all like the needs of backup encryption (deduplication, for instance). This is one of the biggest things wrong with the PGP model of retrofitting cryptography onto problems, and why it has virtually never been successful at any of them.