The "just" is your explanation there. Most businesses want a blog, but also a half dozen other things. An event calendar, a mailing list, contact forms, an online store, etc, etc.
WordPress is kind of a mess technically, but you'd probably be surprised at some of the name-brand sites that use it. I want to say the NYT was using it at some point. It's the epitome of "don't let perfect be the enemy of good enough". You could build a better site by duct taping together a dozen services or open source products, but WordPress is generally good enough.
It’s not perfect but its easy to use and a lot of people know how to use it.
We switched our non profit to using it so we could have more people helping post content. We could teach something else, but this was fairly easy..
Have a favorite one? (Not a list of ten, please, just one or maybe two.) I've found WP easy & pleasant to use for my personal blogs, but I'm open to switching to something that's better and not associated with this nutbar.