I realize the title is just a hook for the (very cool!) work in the article, but a couple things that tarballs don't/can't specify that Docker containers can:

- environment variables like locales. If your software expects to run with English sorting rules and UTF-8 character decoding, it shouldn't run with ASCII-value sorting and reject input bytes over 127.

- Entrypoints. If your application expects all commands to run within a wrapper, you can't enforce that from a tarball.

You can make conventions for both of these like "if /etc/default/locales exists, parse it for environment variables" and "if /entrypoint is executable, prepend it to all command lines", but then you have a convention on top of tarballs. (Which, to be fair, might be easier than OCI—I have no particular love for the OCI format—but the problem is harder than just "here are a bunch of files.")