From what I understand, it's not that they are integrated. Those apps allow to send and receive SMS. In doing so, they can simply send the queries via SMS on those apps, allowing to receive the result there.
Edit: I was wrong!
Edit: I was wrong!
If you use those, you'll see that the responses are almost instantaneous, compared to the lag which SMS inherently has. There is a general purpose API that can be used via any platform - Slack, Telegram, Gtalk, or email. Anything that supports text.
When you say "natively integrated" what do you mean? As far as I can tell there are no APIs for either Whatsapp or Facebook Messenger.
I'm using thirdparty open source libraries to integrate FB and Whatsapp into this.
User interactions have really spiked as we speak. Try shifting to FB Messenger (if abroad or not wanting to use SMS) or SMS in the meanwhile!