You’d be swapping an open-source vendor independent API for a cloud-specific vendor locked one. And paying more for the “privilege”
EKS isn't any cheaper either from experience and in hindsight of course it isn't, it's backed by the same things you would deploy without EKS just with another layer. The dream of gains from "OS overhead" and efficient tight-packed pod scheduling doesn't match the reality that our VMs are right-sized for our workloads already and aren't sitting idle. You can't squeeze that much water from the stone even in theory and in practice k8s comes with its own overhead.