I imagine it's a lot of hassle to maintain and outside of the US SMS is basically as dead as landline phones. They probably consulted their usage statistics when they made that decision.
Why? It hasn't changed in years. It's easy to use and glaringly obvious that it's a non-secure conversation. Sometimes I go to add a reaction to an SMS conversation before remembering that those don't work on SMS - the only problem I have ever had with it.
> outside the US
that's a 330m-person population, which is also home to Signal. Not only do I get SMS from people like neighbors and so that I don't especially want to convert, SMS is used to send payment receipts/pickup notes in restaurants, 6 digit verification codes for many websites and so on. If you are outside the US and don't have to deal with SMS congratulations, but for the large number of people in a territory where it is still a key part of digital infrastructure, arbitrarily yanking the feature is a huge pain.
It has though. RCS has come along, which means that you might send an SMS to someone, and their response gets "upgraded" to RCS. If your app doesn't support RCS (and it's impossible to support RCS right now, because the APIs aren't available), you'll never see it.
The choice is between "Keep maintaining the functionality and have people get progressively angrier that their messages are going missing" or "drop it entirely".
Probably because it is dead in a large number of places (e.g. I haven't used SMS in the last 10 years for anything except these automated things that sometimes are sent), and people tend to generalize that to "outside the US".
> outside the US
that's a 330m-person population, which is also home to Signal. Not only do I get SMS from people like neighbors and so that I don't especially want to convert, SMS is used to send payment receipts/pickup notes in restaurants, 6 digit verification codes for many websites and so on. If you are outside the US and don't have to deal with SMS congratulations, but for the large number of people in a territory where it is still a key part of digital infrastructure, arbitrarily yanking the feature is a huge pain.