I think these companies are failing to implement STIR/SHAKEN and are running into expiring grace periods. That's not necessarily evidence of guilt - they might claim that as a small business they cannot afford these changes - but it seems like the only option to clean up the mess caused by spammers.

The protocols are meant to allow tracing which network originated a call - at their root is an attestation by the network that a call they are originating for one of their customers is allowed to use the number in caller ID. If you're a network who wants your originating calls to be carried across other networks, you can't just set up a promiscuous attestation system that allows your customers to just slap on any random caller ID that they want, or else you'll get blacklisted real quick.