The big argument for getting non-geek friends and family members to get Signal is "take this app, nothing will change for you, you can still SMS the way you did before, but you will have better privacy". Early versions of Signal could also import SMS, so it really was transparent. Well, mostly, there was still some issues they could have addressed, but didn't.
You can't use that argument anymore, the most likely reaction you will get is "I already have too many apps, I don't want another one, it is too complicated". Or you may install them Signal, and they proceed to send you another SMS, because that's what they always do, and it works, and they still have their SMS app. Or they already have WhatsApp, and so do you, and they are perfectly happy with it.
Really, for me SMS was the little thing Signal had that could help its adoption by the public at large.
The most compelling bit here for me is RCS. Lots of devices will auto upgrade an SMS chat to RCS if they think that both ends support it.
Signal cannot support RCS (there's no API) so you'd end up with a situation where someone uses signal to send an SMS, the recipient device then replies over RCS and signal never gets the reply. Not great for usability.
The big argument for getting non-geek friends and family members to get Signal is "take this app, nothing will change for you, you can still SMS the way you did before, but you will have better privacy". Early versions of Signal could also import SMS, so it really was transparent. Well, mostly, there was still some issues they could have addressed, but didn't.
You can't use that argument anymore, the most likely reaction you will get is "I already have too many apps, I don't want another one, it is too complicated". Or you may install them Signal, and they proceed to send you another SMS, because that's what they always do, and it works, and they still have their SMS app. Or they already have WhatsApp, and so do you, and they are perfectly happy with it.
Really, for me SMS was the little thing Signal had that could help its adoption by the public at large.