Why would i want to run my database in k8s?
Because kubernetes is a fantastic platform that provides a lot of node and app management functionality out of the box. Stateful services like databases are not really a challenge anymore given recent developments in both K8S and database containerization.
People say this but my first reaction to "let's put our DB in the Kubernetes cluster" is still to take two steps backwards and prepare to run in the other direction. It really goes against all of my better instincts (and unfortunately hands-on experiences).