All the Apple apps that are pre-installed on an iPhone have a massive advantage over third-party options in the App Store. Most users just stick with the pre-installed Apple apps for email, web browsing, using the camera, looking through photos, and taking notes. There used to be third-party flashlight apps in the app store, but Apple used their platform power to crush those apps when they included flashlight functionality for free in iOS 7.
Of course, one can argue that Apple has used its platform power for a worthwhile goal - creating a better user experience. People made a similar argument about Walmart back in the 90s and 00s when they were in the news for crushing small businesses - it's fine because Walmart is just trying to give customers lower prices.