Yes and no. The problem is that if you make a call from AT&T then AT&T knows you made the call. But AT&T also has to treat calls from other carriers - including carriers from other countries - as valid phone calls, without knowing if the information provided by the other carrier is accurate. Most of these spam factories are based offshore in countries with lax regulations. Others use legitimate services like Twilio to launder their calls so you have to subpoena their carrier, then subpoena Twilio only to find out that the call is coming from a country or jurisdiction where what they're doing isn't illegal. It's a slow and painful process to track these scammers down.

Sure, but that doesn't necessarily do all that much to stem the tide. The spam callers care a hell of a lot more about maintaining access and call volume than the telcos care about ensuring spammers stay off the system; if they don't have multiple redundant systems run by facially independent cut-outs, they're organizationally incompetent.

Like, employing someone to hire people off craigslist to help "set up their new business" by opening an outbound phone account under the craigslister's name is cheap compared to the gains from running the spam network.

The phone companies know, but they won't tell you without a court order.

"We traced the call. It's coming from inside the house!"

Telcos make a bank facilitating the spammers.