WooCommerce is based on WordPress
Currently 20% of websites WORLDWIDE run on the WordPress CMS software platform. Add to this the fact that WooCommerce runs on over 600,000 stores.
WooCommerce was Purchased by Automattic
WooCommerce has a Healthy Ecosystem
While the core WooCommerce plugin is free the Extensions needed to customize the cart system in order to handle your specific business are not. This allows you to choose in and ala carte fashion just the Extensions that you need in order to get your store up and running.
WooCommerce fits like a surgical glove, not an oven mitt
Because WooCommerce exists in the WordPress universe it is highly customizable.