Love it or hate it, Facebook has built a great feature set into a very well-performing app in Messenger. And combined with the crazy-big user base, it’s getting harder every day to justify not using it (or at least having it installed).
-androidguys.com-

Facebook Messenger is an excellent mobile chat client that connects you to the billion-plus Facebook users from your iPhone. It's a complete package, offering text, voice, video, payments, and now secure, secret messaging.
-pcmag.com-

If you want to communicate with your customers, building a Facebook Messenger bot is a lot cheaper than building a mobile app. The second advantage is that the field is still wide open. While Facebook has 6 million advertisers, there are only 300,000 chatbots. That’s a lot less competition.
-blog.hootsuite.com-