I'd normally also have to select packages for sending emails, running background jobs, internationalization, templates, validation, file uploads and caching at a bare minimum. Then I'd have to make sure they all work well together, setup testing and probably have to write additional functionality that Rails or Django already covers.

Frameworks like Rails and Django cover a ton of functionality and gluing together and maintaining a set of packages to cover even a fraction of that functionality is a ton of work that's often for very little gain.