[ralph87]

This idea is common but a strange one at least to me. Going back to GSM would of course be a regression due to their repeatedly broken crypto, but modern LTE networks have many desirable properties absent from Internet-based messaging.

Perhaps it matters less to a US user, but as a European the fact an intra-country communication need not traverse any border nor be observable by any non-domestic entity is a huge deal for me, due to much stronger data protection laws in these parts covering both message content and metadata

Then there is the trustworthiness of the communication medium itself. WhatsApp is being advocated in this thread, but WhatsApp is a massive chunk of unaudited code running on your handset that is published by an advertising company, code that by design steals your phonebook without telling you every time you run it. At least in the UK, telecom providers generally act for the most part as commodity infrastructure, we don't seem to have quite as many scummy behaviours as are reported in the US. Both approaches require a central counterparty with either absolute trust to protect your cleartext message in transit, or provide otherwise unaudited code claiming to protect the same.

The bottom line for me is probably who gets to keep the metadata, a US advertising company or a local telco. I am certainly happier with the latter.

[antihero]

I mean people get repeatedly owned through SIM swapping either due to socially engineering the absurdly poor security of the telcos or buying access to the zero security internal network (SS7).

[Nextgrid]

IP-based communication doesn't mandate giving away control to a third-party. The advantages of GSM-based communication that you mention are totally possible with IP-based communications, and in fact in pure LTE networks (without 3G/2G fallback, also called CSFB), "standard" phone calls and texts are actually carried over IP (towards a SIP server hosted by the carrier).