You can get resilience from hardware failure and shorter downtime windows if a host needs to be rebooted since the database will immediately start up on another node.

A good Kubernetes cluster will also give you centralized logging/monitoring/alerting as well.

So if you already have a cluster (and an administrator), you do get benefits. But the benefits are only really worth it if you can amortize the cost of the cluster administration over many applications.

I’ve seen some companies using development clusters and assigning namespaces per user. With MSSQL being able to run in containers they’re able to spin it up quickly and point it to a sanitized version of their production data. If they update MSSQL it’s just a matter of killing and spinning up a new container. Or you want to test an update just spin up the new version, point it to the same data, and run your tests.

Even databases like MySQL and PostgreSQL do scale out for HA reasons--they have multiple replicas. It's easy to set this up on in Kubernetes, especially for databases that have operators.

One of the main components of systems like K8S is a distributed database, such as etcd.