My personal opinion on this is that Docker's application of Linux namespaces+cgroups happened to solve a specific problem - reducing differences between prod an

My personal opinion on this is that Docker's application of Linux namespaces+cgroups happened to solve a specific problem - reducing differences between prod and dev and doing stateless deployment - in a way that is pretty simple and didn't break people's expectations for how Linux works. Prior to that, namespaces and cgroups didn't have a "killer app".