But how many people actually reset phone and reset data? I'd imagine a lot of people simply manually delete their photos and unhook their Internet accounts from the phone. Hardly a wipe.
But it's so easy to do on iOS. You can do it on the phone - Settings->General->Reset
And it wipes the phone - the flash storage is encrypted. Resetting it wipes the key and generates a new one. It then reboots and reformats the user storage using the new key and mounts it. The old data is irrecoverable because the key is lost, and the new data is written using a new key.
Even prior to encrypted storage, iOS3 created the option to do it where it erases and wipes the storage - anything 3GS and newer wipes keys (so wiping takes a couple of minutes), older ones took a couple of hours.
No reason Android can't do the same - either by sending TRIM commands to the entire user storage area and then forcing a write-all-with-zeroes to be doubly sure.
Android CAN do the same by simply performing a factory reset.. apple hardly had a fucking monopoly on factory reset functions in phones.
it's just that most normal users haven't a fucking clue and thus don't reset their phones to factory state and that's where the problem lies.