Drupal's modular system allows you to start your site simple knowing you can easily build it into a large web application or e-commerce site if needed. A Drupal site will future-proof your business’s presence on the internet.
Commerce Guys have created an amazing set of modules that can give your site robust and fully customisable E-commerce functionality. Like everything Drupal this is completely free.
Drupal is an open source product. This means that there are no licensing fees. It also means that the wider community is able to contribute additions and improvements back to Drupal.
Drupal core code is well crafted and designed. However things move fast on the web and Drupal allows for easy updating. To keep up with the ever changing web Drupal is constantly evolving with the core software now nearly up to it’s 8th version.