Why wouldn't you? If you decide to not use a PaaS and self host your own servers would you reach for a VPS or would you manage your own rack in a colocated data center?
Precisely, it's just about which abstraction and responsibility level you want to engage with. Managed k8s (from good vendors) means the scheduler is as far as you need to go which is enough to do a great many "self hosted" things.
