Many people own a root-server and want to use it with multiple domain hosting for email, webserver and a MySQL-database. Most of them use the console and their favorite editor. No one needs more!
But: If you want to lease parts of your server (e.g. webspace service provider, email service provider), the more complex becomes the setup. Furthermore you want to provide your customers the possibility to manage their domains, email addresses and ftp accounts on their own.