Earlier quoted context omitted.
But realistically I don't know why any carrier would give a damn about this. In 2013, SMS was already irrelevant in most of the world. And in the US pretty much everyone had had unlimited texting for a while. Encouraging people towards OTT messaging was beneficial to carriers that were now ubiquitously making money on data packages, not texts/calls.
End users are not the only customers for SMS. A large number of automated notifications, confirmations, and 2FA codes are sent that way, and carriers get paid for it.
Not just paid, they gouge their enterprise customers for it. Signal did a cost breakdown[0] and of their $13.7 million infra costs, a whopping $6 million is "registration fees".