There are a lot of things that are appealing about using wordpress to build a site, but I think its mostly ease of use. WordPress does all the heavy lifting for you. You don’t have to understand HMTL or CSS to make an attractive, usable wordpress site. It’s already scaled fore mobile sites, there are plug-ins for whatever you need, and it’s easy to update. If you want to change the look of your site, but preserve your content, wordpress makes it easy. Plus, it’s open source, so it’s constantly being improved.
There’s a huge learning curve with HTML and CSS, but wordpress does all that hard work for you. It’s much easier to use.
There are a lot of people using wordpress. As of January 2015, over 50% of CMS sites were built with wordpress – nearly 16 million sites. I’m not sure how many were used for business versus being used as personal blogs, but the numbers are staggering. https://www.codeinwp.com/blog/wordpress-statistics/
As of March 1, 2017, WordPress boasted 58% of the CMS market. It’s nearest competitor, Joomla, had only 7%. https://w3techs.com/technologies/history_overview/content_management
I found a bunch of really great wordpress themes, but here are my top 4 free themes.