It's in their best interest not only not to secretly collect user information, they also want to show that they care about stuff like that (because then they can point their finger at others).
Apple cares about credit card info (because that allows them to let their customers easily pay for everything, it lowers the barrier), but Apple doesn't have to covertly collect that, they are far too popular to need such shady tactics. And that's about it. iAds might matter, but it seems to be a flop and Apple isn't exactly heavily invested in it.