That's very cool, thanks! Note that this allows selectively creating Kubernetes resources backed by GCP resources. Looks like it will not automatically sync everything that already exists, which seems like a missed opportunity.
To expand on what Brendan wrote, Kubernetes does a lot more than just run containers. It provides container-centric infrastructure and a platform for building robust automation.
In a VM-centric world, one wouldn't just use raw VMs in production, but would also use managed groups, load balancing, autoscaling, DNS, Spinnaker, etc. If one manually pins specific containers to specific hosts, IaaS APIs and tools can still be used directly. When dynamically scheduling containers, that doesn't work.