They likely get more in return that we're unaware of .... But, you know -- they gave the same kind of info (and much, much more) to firms like Cambridge Analyt

They likely get more in return that we're unaware of .... But, you know -- they gave the same kind of info (and much, much more) to firms like Cambridge Analytica for free for years. So perhaps they didn't even get more in return. Facebook's purchase of WhatsApp was OKd by EU regulators subject to some constraints, e.g. that they don't use WhatsApp data to enhance FB graph and/or gain other unfair advantages. FB has since admitted to using WhatsApp metadata in violation of that constraint (and didn't even get a slap on the wrist) - and perhaps giving the data to Google is also part of playing dumb. I don't know, but I'm sure it has everything to do with benefit for FB and GOOG, and almost surely at the expense of user privacy.