It seems to me like you're being downvoted because it looks like you're making the "nothing to hide" argument. But a more charitable interpretation might indicate that you feel SMS still has utility despite being unencrypted, which I agree with.

If you have someone's phone number, you can just about guarantee that you can message them. It might not be encrypted, or have richer features like other messaging services, or it might even be expensive, but it's fairly reliable and doesn't require any third-party apps. Just like how you might shout to someone at a distance to get their attention and convey important information, but you wouldn't shout their credit card number to them.