I may be naive and eventually end up with egg on my face but here goes. In today's world we all know the horse has left the gate wrt privacy. It seems the issue now isn't who's collecting the data, it's what happens to your data after it's been scooped up. And what keeps the data from escaping comes down to the question of how that data is being exploited for generating revenue.
Google gets a lot of flack around here but if you follow the money, they have a pretty good incentive to do whatever it takes to keep the tracking data high-quality and most definitely in-house. Mainly because they own the search market and the better the ad targeting, the more protected Alphabet's revenue stream is.
Apple is obviously dependent on hardware sales so not much needs to be said about that. Plus they really don't want bad PR from data escaping.
So let's compare that to the other 800lb gorilla(s). I don't see any reason why Facebook, Pinterest, etc. wouldn't incorporate outright sale of their tracking data to third parties (if they don't ship it out the back door already). Sure, they're dependent on ad/affiliate revenue too but with one other important difference. Google has an (effective) search monopoly where data exposure would stir up a hornet's nest of legal issues directly or indirectly.
So what's keeping Facebook from transforming more of their revenue stream from ad sales to data sales down the road? Especially with the ad controversies that were swirling around (https://youtu.be/oVfHeWTKjag)? Following the money...not much?
P.S. - s/tailer/tailor