Imagine you are the developer of k8s hosted systems. Now imagine you want to test your systems in a repeatable fashion. You'd need some way to spin up a test k8s cluster, deploy your application, subject it to a test workload. That's simple and easy if you only need one physical cluster node: you can use k3s or perhaps kind. But if you want multiple physical nodes, not so easy. This solves that problem by leveraging an existing k8s cluster, which is a standard thing easily obtained. You might now ask why not just use that cluster (why the terduckin?) Answer: cost, time, hassle, you want a different version of k8s than the hosting provider gives you.