The answer was not SMS. It was "Big Tech". There is a belief that these so-called "tech" companies want to collect data and analyse communications for commercial purposes in ways that telecom companies never did unless they were hit with a subpoena (and that's still not commercial use). Unlike telecoms, these companies have not had to operate under significant government regulation (including laws concering customer data), their original business model is surveillance-based advertising and they are unlikely to abandon it. (Telecom companies have obviously morphed somewhat in response to Big Tech's competition, arguably not in a good way. This evolutionary pressure toward surveillance for profit is a more subtle form of the threat posed by "Big Tech".)