I am not sure how you think health insurance companies or Netflex are monetizing customer data.
Data brokers pay good money for such data, which they can then sell on to anyone who is interested. And there are literally hundreds of data brokers out there, all collecting as much information about you as they can get their hands on. Every single data point, from your medical diagnoses to the movies you like to watch, adds to your profile and increase both the number of interested customers these data brokers have and the price they can charge those customers.