They didn't totally fail to monetize it:

https://www.engadget.com/2019/02/07/carriers-were-selling-yo...

> Carriers sell information about you to data aggregators, which normally require the user to consent before selling it on further. But some third parties opted to sell information, like people's whereabouts, on to bodies such as bail bond companies, bounty hunters and landlords. In its original report, Motherboard paid an bounty hunter $300 to get the location of a phone to within a few hundred meters.