The problem is once you add this functionality, the cat's out of the bag and replies to requests to further invade users' privacy on-device change from "we can'

The problem is once you add this functionality, the cat's out of the bag and replies to requests to further invade users' privacy on-device change from "we can't" to "we won't", a position Apple can't possibly hope to maintain, esp. with the likes of China or the US government.