Right, but it goes from being something you get for free to being something you have to go out of your way to do. Which can matter, especially on projects where you're designing a site/theme to hand off to someone less technical.
I've found that using the same class name for styling and attaching behaviors to be dangerous... refactor the styling and lose the functionality, or break the tests, or disable the analytics.
I'm glad that backbone and jQuery apps are in my rear view mirror at this point.
The reason why you're finding this dangerous is because you've coupled your class names too closely with your style. Class names should describe what the content is about, and so if the class names change, that implies that the content itself is different.
