Oh, I’ve used SuperDuper for years, and I adore it. Several years ago I had a spinning rust HD die in a Macbook. I plugged my backed drive into it, booted, and had access to all my stuff. Without that drive I would have needed another computer.

I could keep going making a list of all the ways I’ve found a bootable clone of a MacOS machine to be useful, but damn, I’d hate to live without it.