I would say the primary benefit of docker is that you can build once, run the same everywhere.
E.g. you have a consistent, reproducible application environment which _should_ be vetted through a gauntlet of continuous integration, testing, etc. that once created will run identically on any host running docker.
If you have a "trusted source" to do all the grunt work for you, fine. But docker's promise isn't guaranteeing a trusted source. It's providing a consistent, invariant application target from developer laptop -> production host.
Well, sort of. Java was never really like Docker, and in fact always struggled architecturally to provide a good container abstraction for applications. The "servlet container" idea was (and is) a failure. Java never had the equivalent of the Docker daemon, and it only (relatively) recently got something like Dockerhub via Maven--and Maven repos aren't integrated with the JVM or the (non-existent) Java daemon.
E.g. you have a consistent, reproducible application environment which _should_ be vetted through a gauntlet of continuous integration, testing, etc. that once created will run identically on any host running docker.
If you have a "trusted source" to do all the grunt work for you, fine. But docker's promise isn't guaranteeing a trusted source. It's providing a consistent, invariant application target from developer laptop -> production host.