[robszumski]

Aside from being faster than replacing all of the hosts, the reason OpenShift does it this way is that you can't just burn down and replace a fleet of bare metal machines. While re-PXEing is possible, this takes a ton of time and stresses that infrastructure.

Doing the same on cloud, metal, OpenStack, VMware, etc means that your cluster's operational experience remains the same and in most cases is less disruptive.

edit: having your nodes controlled by your cluster has a number of other benefits aside from patching, like the Node Tuning Operator that can tweak settings based on the types of workloads running on that set of machines.