I don’t have the EU perspective, which might be changed by things like GDPR, but I prefer Apple’s stance that “no one should have this data, not even us”.

One reason is that the data on a user’s phone isn’t solely owned by them. Some of it is shared with other people, or “belongs” to someone else: chat, email, shared documents, photos of people, contact information, etc.

In a corporate environment, this is more explicit: you have access to company information, so the IT department controls what apps you can install / run, because individual EEs won’t always make the best choices.

Second, I think app developers are more likely to share more data, if they know that the shared data doesn’t leave the user’s control. And that (presumably) makes the feature work better. If I’m developing an app, I’ll think twice about indexing any sensitive data, if I don’t know where it was going to end up.