Most if not all IDEs separate compilation from the actual editing. So choice of editor is really orthogonal to whoever is doing the compiling. Ideally you want to be able to do this all from the command line anyways so you can run automated tests when code is checked in. Vim and Emacs can be set up to emulate a pretty convincing IDE experience, but the separation between editor and compiler is much more clear.

To reverse your question: why require an IDE if the same tools work on the command line too?