Advertisers also want to actually get that private data, so they can refine their targeting. And then of course there is the problem of leakage (Cambridge Anal

Advertisers also want to actually get that private data, so they can refine their targeting. And then of course there is the problem of leakage (Cambridge Analytica et al). So it's not quite so benign as you suggest. Every marketer I've ever met has a voracious desire for any/all data about anyone they might consider marketing to.