Recovering data from iphones that don't turn on .. why is that even needed ? In the Apple ecosystem everything is live backed up to your iCloud. If the hardware fails or is replaced: it restores from the cloud.
It's quite common for people to 'think' it's on when it's actually off and only find out when they need it and go to use it.
It's strangely common, as if the setting sometimes turns itself off for some reason.
The number of people that say "I was sure that was on" after loosing data is too high to be just from people actively turning it off for some reason, because there isn't any reason to do that. It happens to much to just be accidentally clicking or from a child paying with the device.