Dan Lages has written a piece on how WordPress is relied upon by a lot of different people and websites, but in most cases it isn't really the optimal solution:
“That’ll do.” I can only imagine this is what was said to the WordPress developers as they bolted website service together with the initial blogging platform. It is clear that the WordPress is tailored towards bloggers, the initial audience of the service. As a result of this, users are left facing an endless amount of themes that prompt the use of posts, not pages. How many times have you seen a blog on a company website?
In fact, every element of the service appears broken without a heavy backlog of blog posts. From the menu system, to an empty archive sidebar that is included by default. The result of this horrendous integration is a collection of un-utilised pages and elements that leaves users with various questions. - dlages.com
I seem to agree with everything he's written, and if you read it for yourself, you can clearly see for yourself why WordPress isn't the best idea.
It may be used a ton, but it really shouldn't be. I for one started to use Ghost recently, and I really prefer it over WordPress.