The current bots trends started when silicon valley saw how successful WeChat is building a platform on top of its chat app. It has an eco that is not tied to AppStore/PlayStore. What WeChat is doing is more of building apps rather than bots on top of WeChat. They took the idea of SMS apps (e.g. SMS to vote for American Idol, SMS to top up your mobile data plan) and model it for chat. So one can basically build an Uber app inside WeChat, and that's what Uber's China competitor DiDi is doing. WeChat users in China can do all their Didi, shopping, order food, buy cinema tickets, book train tickets, payment, online banking all within WeChat app. Fast forward few years to 2015, and Slack bots become a thing. So interactive apps via text commands become bots as it gains more intelligence (or not like the case of Tay by Microsoft). Facebook is doing catch up and apparently it is different from WeChat. One crucial thing that made WeChat so successful is payment, and that enables commerce via the platform. There is no such option in Messenger. Maybe not ready or Facebook has a different direction for its bots platform.