Word press is free to use to use, easy to install and flexible enough to do any customization and fun to work on. I think these are the reasons due to which word press is gaining popularity for ecommerce based site.
 

A Few Easy steps to construct your standard ecommerce site

full tutorial at : PSD to Wordpress Tutorial

https://www.squidoo.com/construct-a-standard-e-commerce-site-on-your-own-using-wordpres

WordPress has been the ultimate platform for blogging in 2010 and it has also evolved into many other areas where people have a need for publishing content. Just to mention a few areas that have previously been covered here on tripwire magazine – WordPress is now used for Question and Answer solutions, for portfolios, as a website CMS, for mobile devices, for membership sites, for making money and much more. With all this popularity there is a really strong community around WordPress creating tons of valuable themes and plugins. Not all of the plugins created are essential for running a blog, Not all of the WordPress plugins created are essential for running a blog. I have compiled a list for you with the plugins most bloggers use right now.

Read the full article at: https://www.tripwiremagazine.com/2010/11/15-most-popular-wordpress-plug-ins-of-2010.html