In my experience, it's more that a small webdev company runs these sites and the client pays $50-200/month to maintain it, maybe do a little SEO, etc.

To recreate the site in another CMS will cost hundreds of more dollars, at minimum, (probably thousands, realistically) and even then: what CMS are they switching to that's easier to use and has as wide a variety of plugins as WordPress? Because I'm not sure that CMS exists.

So the conclusion is: why switch? WordPress is perfectly fine for these people.