Comment by sam_goody

Time Machine does not backup your desktop and other spots that might be essential in case of needing a backup. iCloud does.

I know users who would prefer not to trust Apple for anything, and only pay for and use iCloud to backup the Desktop [and similar locations]. If they were to hear that their opt-in for iCloud means that Apple starts copying random things, they would not be happy.

[OT, I use Arq. But admit that iCloud is simpler, and it is not apples to apples.]

IMO, the fact that Apple backs up your keychain to the Mothership; and that this is a "default" behavior that will re-enable itself when shut off, reflects an attitude that makes me very distrustful of Apple.