When they dropped sms support I was no longer able to convince people to migrate to signal.
Before I could make the argument that you need one sms app anyway so that app might just as well be Signal instead of the one that comes preloaded with your phone. That way people would gradually get more and more secure messaging as time went on. When sms support was dropped, Signal could not replace an existing app and adding another messing app is much less appealing than replacing one.