I guess throwing away your key asset is not in the interest of Google or Facebook. I presume Cambridge Analytica only got so far with Facebook because Facebook didn't realize the potential value of its user data till then. Now they'll engage in the same act themselves.
I am a vocal Google critic, but I have yet to see any evidence of them selling my data. Unlike a number of other companies and organizations Google serms to have realized long ago that they are totally dependent on user trust.
I'm not saying they are smart (judging by the ads they have sent me the last 13 years, the killing off of Reader, the nymwars and then killing off Google+ after it turned out to be nice) or nice (the way they keep trying to crush the open web, the "embrace, extend, extinguish" model of pushing Chrome relentlessly until they almost have monopoly, then try to remove the possibility to run adblockers etc etc)