Why do we need an extra Loadbalancer at all?

[schlichtanders]

I am wondering, why you need either Hetzner or Klipper Load Balancer.

I started using Kubernetes in Minikube and the ingress worked pretty fine. My naive understanding was that the ingress nginx (or what you use) is running inside Kubernetes and can be addressed directly, i.e. that it has a stable IP which we can point our DNS to.
This must not be true, if an extra Load Balancer is needed - what am I overlooking?

Little followup question: What is the difference then between using Hetzner LB or Klipper LB?