When I was first investigating Node frameworks for building an API, documentation generation was a hugely important feature that I needed. I was building a public API for a proprietary system at the time. Without good documentation, this, or any API, wouldn't garner much usage as you can probably imagine.
As the initial writing of API documentation is a huge chore, one which I don't enjoy anyway, the even more time consuming task is to constantly try to update documentation to keep it in sync with the latest version of the API. For an API under constant development, this would become a huge time sink, and so drove the need for documentation generation. In most frameworks, this generally comes from requiring annotations, and/or compromising the flexibility of route configuration, which aren't great options.
Fortunately, the configuration-over-code approach of hapi lends itself quite well to being able to generate documentation, as we can generate a full routing table...