One theory is that they are getting ready for E2E encryption of iCloud photos. Apple will have zero access to your photos in the cloud. So the only way to get the authorities to accept this new scheme is that there is this backdoor where there is a check client-side for sexual predator photos. Once your photo pass that check locally, it gets encrypted, sent to the cloud, never to be decrypted by apple.

Not saying it will happen, but that's a decent theory as of why https://daringfireball.net/2021/08/apple_child_safety_initia...