I agree that for many, their smartphone is already the primary computer and they rarely use anything else, except for when doing “serious work”.
As for backup, I think Apple has failed miserably. I have a Macbook Pro, an iPhone and an iPad. I have both IOS devices configured to automatically sync to my Macbook over wifi, but it rarely does so, I have to force a sync for it to happen. Backup to iCloud is a not a real solution. I got a 64GB iPhone, I get 5GB of storage space? Seriously Apple? Given their insane profits and focus on details and that stuff should “just work”, the least they could do was to include icloud backup that fitted the amount of storage on the devices they sell. Their iCloud storage plans doesn’t fit the storage sizes of their devices either. In short, backup just doesn’t work. It should be included and painless. It’s anything but.
As an addition: On OS X you got Time Machine, but that’s only half a solution. It’s only local backup. You need both local and remote backup to have a proper backup. Again, it’s something Apple should really make effortless.