CMSs are clunky, complicated things, especially if you simply want to edit a bit of text on a web page. They also pose a technical problem: What if, for example, you’re making a site for a client using WordPress and they want to edit something in the footer?

This can be difficult when you’re showing someone their shiny new site and they point to the text and ask (quite reasonably) “How do I change that?”

You could add another field to the Settings → Miscellaneous menu, but that also means adding stuff to functions.php and explaining it to a client, on top of all the other stuff they need to remember. To change a simple bit of text we’d be adding an abstract layer to their mental model of the website. Oh, and they’ll probably pay more for this solution.

Far better then to use an on page editor, such as Unify. Obviously, complex sites will need some sort of database mangement system, but for smaller businesses we should be looking at keeping things as simple as possible. A CMS should only be used when absolutely necessary, as a sort of last resort.