There are definitely ad supported apps on iOS, they also control the core of all browsers on iOS. Neither Apple or Google really sell data externally, they serve ads to their audience using algorithms trained off vast quantities of user data. Selling the raw data is a bad way to do it because you don’t have control over it after the first sale. Keeping it internal and selling your services is a much more lucrative way to do it if you have a big enough platform. Chromium is google’s way to spy on you online and serve ads, webkit is apple’s. Google allows non chromium browsers on android but apple requires that all iOS browsers are basically just a reskinned safari.