Apple is strict about requiring apps to get permission to access certain parts of the iPhone, including your camera, microphone, location, health information, photos and contacts. But Apple turns more of a blind eye to what apps do with data we provide them or they generate about us — witness the sorts of tracking I found by looking under the covers for a few days.
A perspective by Geoffrey A. Fowler published on May 28, 2019: https://www.washingtonpost.com/technology/2019/05/28/its-middle-night-do-you-know-who-your-iphone-is-talking/