[jayd16]

Containers are powerful because they solve many computing issues, one of which being able to act as a (lower case c) static container for dynamically linked apps as well as cross-language, multi-executable meta-apps.

Containers also provide many forms of isolation (network, file system etc.), they provide a modern versioning and distribution scheme, composibility (use another container as a base image).

All of these things can, and perhaps should be, done at a the language level as well but containers also work across languages, across linking paradigms, and with existing binaries.