The vast majority of what FB saw (and used to optimise) was first open as a proxy for install, and purchases because they make companies money. Apple have all

The vast majority of what FB saw (and used to optimise) was first open as a proxy for install, and purchases because they make companies money. Apple have all of this data (in fact, it's automatically collected and much better quality) because they own the platform on which the data is collected. Therefore, Apple can supply the same services as FB (on iOS only, obvs).