I ran through the same thing too. I used to work for Opscode. I joined them because I like the idea of "infrastructure-as-code." I remember when Docker came around, I was scratching my head. There was a part of me that thought it has something, and another part that was thinking, why would anyone want to use this? Wouldn't this set us back to the time when infrastructure is not code? I couldn't put my finger on it. And what's really funny is that the "container" metaphor explains this well -- and I had spent time reading up on the history of physical, intermodal containers and how they changed our global economy to boot. The primary point of intermodal containers isn't that it isolates goods from one merchant from another; it is that there is a standard size for containers that can be stacked in predictable ways, and moved from ship to train to truck quickly and efficiently. You are no longer loading and unloading pallets and individual goods; you are moving containers around. Package management. A lot of logistics companies at the time didn't get this either.

Most of the literature out there explains Docker as virtualization, or some confused mish-mash of "lightweight virtualization", or "being able to the move containers from one machine to the other." They pretty much circle around the central point of package management without nailing that jelly to the wall.