Google Cloud Platform Free Tier appears (please verify this for yourself) to provide the ability to run a(n admittedly miniscule) Kubernetes cluster for free. So, why do this? It provides a definitive Kubernetes (Engine) experience on Google Cloud Platform that you may use for learning and testing.
Kubernetes Engine the master node(s) and the control plane are free.
Kubernetes (i.e. Compute Engine) nodes potentially incur charges including for the VM runtime and any attached storage, snapshots etc.