Where does the belief in the tech come from? Are there any examples of real success with this tech?
Bots can't solve discovery in a novel way without big advances in NLP. There doesn't seem to be a bridge from here to there where it makes sense as a user.
Is this just irrational exuberance?
I'd love to understand why microsoft/google/facebook are all continuing to bet big here.
Because they can afford to. And because if you wait for success examples, you might just be too late.
That being said, I actually haven't seen a successful implementation of a full transition from a hybrid to a chatbot example (maybe like x.ai or something, but nothing on a large scale). Think there is really good opportunity there for some basic tasks, but still see bots as glorified menu options for the time being.
Having worked at 2 of the firms you listed above and doing some deep V1 bot explorations for one of them, the immediate idea for bots in the short-term is to replace apps (which is not the best UI interaction model for tail-end apps)
If so, I think Apple's approach in iMessage widgets is fantastic: If you send third-party content to a person that doesn't have the plugin installed, they'll also get a link to install it. So it boosts word-of-mouth.
My sense of discovery was meant in the UI sort of respect. When a feature is hidden from the user, that feature might as well not exist.
Bots (and command lines, for that matter) are awful unless you know exactly what they're capable of. There is an extrinsic knowledge you need.
That is, you can't expect a bot to know whatever you throw at it but you're unsure what you /can/ expect it to know.
The problem is that command lines are sort of made for the expert users whereas bots are said to be the opposite.
Whether that's a viable UX strategy is still up for debate.