When I first started with Joomla!, one of the largest hurdles I faced was the lack of any sort of development environment.  You always want to avoid making layout changes or any other major work ona  website on the live server.  It would be great if Joomla! had a dev feature- maybe we'll create and package one as an extension!

But anyways.  There are other benefits to running Joomla! locally, other than having an actual development environment- you have the ability to work on a fully functioning version of your site without the need of any sort of internet connection, plus it's faster!