As Docker provided a simplified model with sensible defaults and a decent toolset for packaging and virtualizing single-node app environments into containers; so people went out and looked for a solution to virtualize multi-app workloads.

Honestly, I'm not sure Kubernetes is it. K8s seems like a leaky implementation detail when what people want is just to virtualize a workload (with similar simplicity to Docker) and have it work wherever the standard 'workload virtualiser' runs.