Its not just big tech, every company does it because they have to. Quite a few just choose to. And many sell your data for the right price. Others fake data breaches and get paid under the table then collect insurance. Its all an ugly game.
Wouldn't be much of a fake if the source were known, now would it?
Fair point, I have no proof of that happening. It just seems like an easy way to sell data that shouldn't be sold for various reasons. If it hasn't happened yet, it is only a matter of time.