Telcos know that authentication is about the only remaining use case for SMS and are not going to turn down the revenue stream.
And it can’t die fast enough, as it’s essentially the same as broadcasting your sensitive information over unencrypted radio.
Apart from security, phone number based user identification is such a half-assed approach and I still don’t get why Signal wants to die on that hill. It’s inconvenient, yet trivial, for anyone to register a second, third or tenth phone number. With a bit more knowledge and inconvenience, even anonymously. It adds so little.