The only large group of people who still primarily use SMS to communicate person-to-person is Android users in the USA.
Every other country has settled on either Telegram, WeChat, WhatsApp or FB Messenger, or other niche apps. These apps work on both iOS and Android and often also Windows. I haven't sent an SMS in probably 12 years. I don't know anyone who has.
It's only in the US that iMessage is so prevalent that Android users have to use SMS, the only other way of messaging iOS devices. And the US is quickly becoming a de-facto iOS only country. It already has more than 50% market share, even 80% among young people.
With the US going (almost) full iMessage and the rest of the world having already settled on another app there simply no point to supporting SMS.
Signal's rationale is just Signal's own reluctance to build an umbrella messenger. And given they do drop SMS, still won't introduce usernames it's very hard to actually sell it as a WhatsApp replacement.
And now, with WhatsApp supporting password protected cloud backups and up to 2Gb attachments, I'd say Signal will loose the userbase it acquired during the hype and Musk tweet.
In fact, during 2020 Belarus protests, Signal did nothing to support it's own operations during internet semi-blackout in the country, while Telegram tweaked their server side to provide at least some possibility to know what was happening in big cities. So what are the values of Signal — I don't even know. But they sure did support pillagers and rioters in the USA.
To be even more brazen, Signal is not Apple. They stopped innovating. And they don't have enough political power to convince people do things the new way. Even their zero knowledge server is worthless. Check out the story on FBI cracking down on the leader of some right wing proud boys type of armed group. They tracked him and then compelled to give up access to Signal.
Their innovation stopped at providing solid cryptography that was adopted by most decent messengers already. And they aren't visionaries with cancelling SMS.
UPD: the funniest part is that the service that drops the SMS support still relies on SMS to provide account registration.
This is just an unprecedented level of sarcasm.
Currently, it looks like they are focusing on social networking features: stories, emoji stuff, better link previews. Basically everything that competition already did. The roadmap is not public, so I wouldn't take guesses as what may come next. But...
..."dropping support of X as a feature" is some kind of new transcendent approach to product development incomprehensible to common earthlings.
I don't agree with your take or arguments, and you seem to keep branching off pejorative comments on their organization and product instead of actually discussing the points. I think the conversation would be more productive if we focus on the same point, i.e.:
* Focusing on what matters most is a good idea, as nobody serious about secure messaging uses SMS
* Your argument: irony-covered "dropping features is not a good product development approach".
* My counter-argument: it **is** a valid approach, why support a feature that was useful in the past, but it is now dying/not aligned with your core value proposition?
* Your other argument: their focus is on social networking, and some disdainful comment that "the competition already did it".
* My argument: how is catching up with well-established user behaviors across other messaging platforms a bad thing?
(edited for formatting)