These frameworks offer rich configuration and are less opinionated than Rails-like or full-stack.
That's where Node.js really shines. The full-stack MVC frameworks are bundled with scaffolding, template engines, websocket and persistence libraries to allow you build real-time scalable web apps.
For those who use rich-client/front-end MVC frameworks (or not) and just need to spin up a fast Node.js REST API server.
Middleware, libraries and static site generators.