> but they're already paying you.

That's not how it works. It never has.

Even in the days of print publications, the publisher would seek revenues from advertisers, subscribers, and they would sell their subscriber data. (On top of that, many would have contests and special offers which probed for deeper data about the readership.) In some sense, the subscriber data was more shallow. In other senses, it was more valuable.

I get what you're saying about shooting themselves in the foot, and I'm sure there will be options for corporate clients that will treat the data collected confidentially while not displaying advertising. I also doubt that option will be available (in any official sense) to individuals much as it isn't available (in any official sense) to users of Windows. For the most part, people won't care. Those who would care are those who are sensitive enough about their privacy that they wouldn't use these services in the first place, or are wealthy enough to be sensitive about their privacy that they would could pay for services that would make real guarantees.