WordPress and Joomla are created specially for content management. That's why both don't contain e-commerce sections (by only installing the CMS).
As time went on, Plugins/Components developers created e-commerce applications for Wordpress/Joomla. But Wordpress/Joomla are not designed by default for e-commerce... Both are the best for managing content. So if you want to use Wordpress/Joomla for e-commerce purposes you will have several utilities never used (such as Articles, Links, Comments, Image Galleries, Users - just some examples).
If you want to make an e-commerce site, I recommend you to use some clear applications dedicated to e-commerce solutions like OpenCart, TomatoCart etc...
Hope this help!