I can see why they would want to hold onto this feature, since it would make their devices incredibly sticky. If you spent a year or two having an AI understand literally everything that happens on your screen, then you'd be hard-pressed to switch to a different platform that lacks that historical understanding. Assuming there's no way to port the data, this would all but guarantee that you're a customer for life.

It's possible Apple could have pulled this off. But MS has shown itself time and time again to be user-hostile and privacy-agnostic.