Routing allows us to express some aspects of the application's state in the URL. Unlike with server-side front-end solutions, this is optional - we can build the full application without ever changing the URL. Adding routing, however, allows the user to go straight into certain aspects of the application. This is very convenient as it can keep your application linkable and bookmarkable and allow users to share links with others.
Routing allows you to:
Maintain the state of the application
Implement modular applications
Implement the application based on the roles (certain roles have access to certain URLs)