So why not kubernetes?

K8S doesn't scale nearly as well due to etcd and latency sensitivity. Multi-site K8S is messy. The whole K8S model is overly-complex for what almost any org actually needs. Proxmox, Incus, and Nomad are much better designed for ease of use and large scale.

That said, I still run K8S in my homelab. It's an (unfortunately) important skill to maintain, and operators for Ceph and databases are worth the up-front trouble for ease of management and consumption.