We create Magento Modules, Zen Cart Plugins, and Premium Wordpress Themes to support and enhance the themes and templates we create.  Whether you use Drupal or Magento, WordPress or osCommerce or any combination of these tools one of the great features is that they all support the concept of add on tools. You don't have to wait for the next version to find a feature you need; you often don't even need to develop the feature yourself and even better you often won't even need to pay for the feature.  While the names of the tools will vary from plugins, to addins to modules - the benefits are the same.