Do you have a list of them or source for this claim? (not that I'm disagreeing with you, but just want to see the full extent of the problem)
"Verizon and AT&T will stop selling your phone’s location to data brokers" <https://arstechnica.com/tech-policy/2018/06/verizon-and-att-...
"Verizon and others call a conditional halt on sharing location with data brokers" <https://techcrunch.com/2018/06/19/verizon-stops-selling-cust...
It's well known now that ISPs can monetize and sell customer data. For example, see https://www.usatoday.com/story/tech/news/2017/04/04/isps-can...