Why use Facebook Messenger?
- is device & OS independent, and
- can be run on multiple devices simultaneously,
- which makes it more flexible than SMS, and
- more broadly supported than iMessage.
- It also has a URL scheme for providing a one click contact button.
Vague and generic updates explanations
Facebook Messenger, at least for iOS, seems to be updated quite often (weekly?), rarely for any specific reason, providing only a frustratingly generic and opaque update release notes like:
We update the app regularly so we can make it better for you. Get the latest version for all of the available features and improvements. Thanks for using Messenger!