Pure Chat Bots or more correctly ICR (Interactive Chat Response) systems are a niche UI for a limited number of use cases.
The more interesting is the App-in-an-App concept and Android Instant Apps.
But experimenting with the new types of UI is a good thing.
I predict that all those experiments with chat bots will lead to the adoption of Multi-modal interfaces (integrated GUI, menus, chat, voice, VR, etc.)
Eventually we'll switch to Neural interfaces using brain-implantable chips.
Currently the advantage of chat bots, that they are much easier and cheaper to prototype and develop than web or native apps.
The agency will charge you $50K for a high-quality native app, but only $5K for the same quality and functionality chat bot.
Another advantage is the free distribution channels: Skype, FB Messenger, Telegram, Slack, Kik, WhatsApp, etc.
If you plan to build a platform or another bot enabling technology, you already late to the party.