Facebook Messenger

 Facebook Messenger  is Facebook’s direct messaging feature on their website, and also a separate native application for iOS and Android that is known to provide meaningless wordy update summaries.

Why
Why use Facebook Messenger?

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!"