My point is that I'm sure the only way iCloud is profitable or even break-even for Apple is if they rely on over-provisioning storage to users of the more paid plans. I started paying for the 200GB iCloud+ plan, and once my photos exceeded 200GB I ponied up for the 2TB plan. Unless I take up a photography hobby it'll be a long time until I get close to that 2TB, and I'd wager this is what Apple expects. Raising that baseline usage with Time Machine backups would mean it would need to be more expensive for end users, either by making iCloud+ more expensive or rolling out a new subscription product.