Having looked into the history of call tracking / blocking, it's pretty evident that major US telcos have very little interest in making marketing calls difficult. However tenuous the association between "marketing" and the actual practice of the scammers, harassers, abusers, and worse generating literally billions of such calls monthly (see: <https://pirg.org/edfund/resources/ringing-in-our-fears-2025-...>, "The monthly average of scam and telemarketing calls increased from 2.14 billion a month in 2024 to 2.56 billion a month through September, according to YouMail").
Having looked into the history of call tracking / blocking, it's pretty evident that major US telcos have very little interest in making marketing calls difficult. However tenuous the association between "marketing" and the actual practice of the scammers, harassers, abusers, and worse generating literally billions of such calls monthly (see: <https://pirg.org/edfund/resources/ringing-in-our-fears-2025-...>, "The monthly average of scam and telemarketing calls increased from 2.14 billion a month in 2024 to 2.56 billion a month through September, according to YouMail").
AT&T's efforts to thwart effective government regulation and mitigation stand out especially. The industry oranisation ATIS (<https://atis.org/>) has been central to blocking any effective action. <https://en.wikipedia.org/wiki/Alliance_for_Telecommunication...>.