Hyper is a relatively low level HTTP library, while Rocket is a web server framework. So Hyper doesn't concern itself with things like routing, authentication,

Hyper is a relatively low level HTTP library, while Rocket is a web server framework. So Hyper doesn't concern itself with things like routing, authentication, state management, template rendering, static file hosting and so on, which Rocket provides. Hyper is only focused on being a good implementation of the HTTP protocol and serving as a base for higher level libraries and applications. You could use Hyper to build a framework like Rocket - though AFAIK Rocket uses its own HTTP implementation. It's kind of like that difference between Photoshop and libpng.