Ghost runs on NodeJS which isn’t available at most cheap webhosters. Also it doesn’t do traditional blog things like pingbacks, trackbacks or webmentions.
BearBlog can’t be self-hosted at all - it says so right on their GitHub’s README.
WriteFreely is a Go binary that - again - isn’t supported on most cheap hosters. Also I can’t seem to find anything about it supporting pingbacks, trackbacks or webmentions. It seems to be more like a one-user Mastodon instance.
It’s the only CMS that runs on a classic AMP stack which is still the standard with cheap web hosters. And since everyone and their dog is using it, you can easily find support and ready-to-use plugins for almost anything.
In the car world, WordPress is your plain old petrol car that just runs, can easily be refuelled and you can get anything repaired at every other street corner. That’s why it is still so widespread.