Because that high-compute job needs to be distributed on many, many machines, and if you're using cheap preemptible instances you have to handle machines droppi

Because that high-compute job needs to be distributed on many, many machines, and if you're using cheap preemptible instances you have to handle machines dropping off and joining in while you're running that single job. It's definitely not something that you can launch manually - perhaps Kubernetes is not the best solution, but you definitely need some automation.