There are various reasons when you might want to disable text input, including:
interactive based experience
no need for text input
We've made it very easy to disable text input across your bot.
To disable text input you need to go to your persistent menu settings page:
On this page, you can add buttons that will always appear to the user, and you can also disable text input.
Now people can't send text to your bot, they can only click on buttons, quick replies and the persistent menu.