For applications that are free on the store, there's no monetization for Apple in the App Store.
Since we introduced the App Store, we've had both a manual review and, in more recent years, added an automated review of every application that's submitted to the store, and then for every update of the applications on the store. Those applications undergo a review by a dedicated team of experts on the App Store side.
There is a limit that we don't go past, which is that we don't surveil our users' usage of the applications. Once the application is executing on a user's device, for that user's privacy we don't go further and take a look at the network traffic or the data that the user is sending. That would seem creepy to us.
We continue to invest on the App Store side to try to have as strong a review as we can. As applications and their behaviours change, we continue to enhance our review to capture behaviours that don't match our strong privacy policies on the stores.