[elicash]

It's not necessarily the only solution, just the one Apple has started with. My guess is that at least in part there are technical reasons, since even this structured approach will require overnight processing (source: WaPo) by Apple.

I do think additionally, in the case for a situation like with your dad, Apple would need to verify that he is the same person that there's hours of audio of. That strikes me as a difficult at Apple's scale.

[nier]

Archive link for mentioned Washington Post article: https://archive.is/CPk7H

[comex]

Note that article says the overnight processing is done by the device, not by Apple itself.