This comes up in just about any conversation regarding iMessage, and it's pretty out of touch with the real world. Apple backed iMessage into the same app that

This comes up in just about any conversation regarding iMessage, and it's pretty out of touch with the real world. Apple backed iMessage into the same app that does SMS, so you can't not use that app, SMS is still relevant. So iPhone users are going to use that app. Now imagine that 90% of your friends and family use iMessage, but not by some deliberate choice, but because they just view it as fancy text messaging. How on earth are you going to convince all those people that they should download Signal, WhatsApp or Telegram? The answer is that you don't. You might get a few people who already use Signal to start contacting you that way, but the rest... they aren't going to install yet another app just because you don't like iMessage, and when SMS still works just fine. But now you're excluded from all group chats and videos or largish images.