There are other services which rely on this header’s information for authentication (which of these addresses did you live at in 2021?) so for approximately $15

There are other services which rely on this header’s information for authentication (which of these addresses did you live at in 2021?) so for approximately $15, you can dramatically increase the effectiveness of an attack on those services. Unlisted numbers have been a white pages paid feature for a very long time. Very similar incentives in both directions compared to these headers, I’m sure. (Yellow pages were pay for inclusion, iirc.)