How about generating a "lifestyle profile" (or psych profile).
They could sell that to a third party, then buy back the profile compounded with other third parties's data to use for advertising. Bonus points if Alphabet (aka Google) control all the companies involved.
https://www.theverge.com/2014/8/5/5970141/how-google-scans-y...
Oh, and for indexing, of course.