I would guess that nothing happened to them, and that they have never been used to store encrypted iCloud data. Apple has an enormous amount of data that needs

I would guess that nothing happened to them, and that they have never been used to store encrypted iCloud data. Apple has an enormous amount of data that needs to be stored beyond iCloud: iTunes, App Stores, Apple Music, etc. I'm sure they store much of that data in-house. There is also the possibility that Apple eventually plans to move iCloud to their own storage solution, but hasn't yet scaled up to it yet.