You don’t see the harm in requiring telcos - famous for handing over data without warrants or court orders - being forced to have identifying data for every subscriber?

I can think of a half dozen ways that can get abused. Remember that in the states policing is decentralized. There is always some department somewhere willing to abuse their power. Look at how flock has been used to stalk partners, or how geofencing was used to sweep up everyone in the area of a protest, or how stingray is used to listen to all calls in an area. This is opening up avenues of abuse for almost no benefit.

Realistically, it is for 99.9% of people who have phones. The 0.1% have to go out of their way to buy, with cash or crypto, prepaid SIM top-ups on flip phones, and by doing so they stand out like a sore thumb.

Back in the days of rotary phones, not only did the phone providers have your name, they even listed it, your home address, and your phone number in the white pages of the phone book, and everyone in town had a copy of it. Before the rise of microcomputers which enabled data tracking and robocalls, which in turn gave rise to demand for privacy from spam, having that information out in public wasn't a problem except for edge cases like domestic abuse victims or people in a witness protection program. The 99.9%, though, are still getting tracked no matter what, and I sometimes wonder if we've sacrificed the convenience and confidence of the phone-book age for an illusion of privacy that relies on anxiety.

The big ones already force you to give SSN for service. Then they lose it in a data breach.

Almost no one has physical phone lines anymore. It also used to be a given because they had to send a physical paper bill to someone, and hence needed an address.

Neither of these are true anymore.

Also, the tone is set from the top.

Do you think the current admin cares about actually tackling fraud and abuse?