You aren't supposed to be moving SSH keys. They should stay on the machine they were generated on. The less accessible they are the better.

I really wouldn't rely on an SSH key as the sole way of accessing a machine.

This works for some scenarios but not other ones. I, for one, deal with ephemeral VMs.

Why not use agent forwarding?

	▲	maratc 5 hours ago \| parent [-]
		Where possible I do, of course, but some compute resources either don't allow to ssh in (e.g. k8s) or are configured to refuse ssh from anyone but root. I can become root on a jump box and ssh from there, but I lose agent forwarding in the process.