IIt's simpky not acceptable that I have to update my device without using my previous settings...
it is true that if my device "lives" only in Apple environment, then I can simply wipe my iPhone and install iOS9 as for a new device...
But the trouble is that many "pro" like me use their iDevices in very complex ststems...
Just to provide an example:
I manage a network of Macs and iDevices, sharing services like iCloud, iCloud Drives, Dropbox, Google Drive, etc.
Even if I decide not taking care of anything but Apple devices, if I erase one of the affected iDevices (let's say my iPhone), I will have most likely to go on ALL the connected devices to re-enable the password keychain...
Sonetimes it's easy, but some of my devices are in foreign countries... So the option is to hire somebody abroad to sit in front of my device and set back the keychain (and I don't trust nobody but me) or I should buy a plane ticket to go there and fix...
If Apple is so kind to pay, I will do it gladly...