I believe this is the same permission Facebook and others require and have stated they use it to allow convenient confirmation of your mobile number. They can a

I believe this is the same permission Facebook and others require and have stated they use it to allow convenient confirmation of your mobile number. They can automatically receive and delete the incoming SMS confirmation message sent from their server to your device. This is a fault of Android's permission system which, while a huge step forward when iOS had nothing, is now very outdated and leads to less security and app function awareness.