Google doesn’t sell people’s data. Neither does Facebook.
Both companies sell ads. Data they collect is used to target those ads. That is their market edge. It doesn’t even make sense for them to want to sell data to 3rd parties because it would diminish their ad-targeting advantage.
I’m not suggesting that there aren’t other reasons to be concerned, but the myth of Google or Facebook “selling your data” is just wrong.
These companies are in such a position, that they have so much data when selling it brings competitive disadvantage.
There is a competition going on from the control of the world, in terms of sophisticated A.I. development. This is where they are using their data. Ads are just little sidekick in the process anymore.
Also, they probably do everything with the data and a bit more than average data buyer would do.