It's my understanding that containerization's major benefit is not for development but for system maintenance. It allows sysadmins the luxury to stop spawning VMs left and right, since you can safely avoid all the overhead of keeping full VMs worth of hardware resources for applications that will ultimately only need them in short bursts.

By itself, containerization is great already, without involving the devs at all.

What Docker attempts to provide is a Framework that allows Devs and Sysadmins the use of the same tools. Ideally, if you can get your devs to use this framework, you will unlock the next step: you no longer deliver sources or packages in production, but rather entire Docker Images, ready to use and with clearly identified interfaces with other systems. It's a dream come true for IT sysadmins, who can focus on their own problematics, monitoring, logging, security, resource management, network architecture etc.

And that's what great about the Docker effort: it's the devs trying to be the best wingmen in the world with their sysadmin pals.