Indeed I forgot the "I've never met you but need we need to make a transaction for some reason (buying a house or a TV second hand), so let's start with SMS which will work for sure".
For anything else, using SMS is like using Notepad to write books. Many better alternatives have come through in the decades since that tech was new.
It feels very weird to have both a very good end-to-end encryption (the Signal encrypted messages) and a very bad system (SMS) together in the same app. People should just move away from SMS, it's not like it's hard.
I have no idea (and not living here long enough). But if I had to guess, it could be that cheap/free SMS texting came before cheap/free mobile internet and thus it was already established.
