The current TC is 3T, and there is no way to recover 3T user data via internet for a normal home user. It's just far too slow.
IMO, iCloud and TC are 2 different market. Of course, Apple should provide time machine function (or easy backup solution) for iPhone / iPad on to the TC, but they didn't. And force the Mac user to use iCloud is too early. The average internet connection quality (and quantity) is not there yet.
For me, I am more than OK, I have 1000Mbps internet connection with unlimited data. But quite a lot of Mac users are with much slower internet speed with data cap. If Apple give up TC now, they will simply force the user to buy external HDD, Network disk, etc as their own backup solution.
Also, not everyone love to upload their own data on to the net (even that's Apple server). For professional, they may not even allow to upload anything to the net for backup purpose. Many user still prefer / must have onsite backup solution, and keep all their data 100% private.
That won't work without a work around. Networked Time Machine backups like that are kept inside a sparse bundle image and will not be viewable to restore when connected directly to a mac over USB. There is a way you can open the sparse bundle image and drag the backups.backupdb actual backup file out of the sparse bundle to the root of the external drive. Then you can access it over USB to restore.Never ending restore is what makes me prefer AirPort Extreme plus an external disk. When you have to, unplug the disk and connect it locally to the notebook