Quotes from Matthew MacDonald

Because HTML is a living language, an HTML page will never become obsolete and stop working. HTML pages will never use a version number (even in the doctype), and web developers will never need to "upgrade" their markup from one version to another to get it to work on new browsers. By the same token, new features may be added to HTML at any time.

All the semantic elements share a distinguishing feature: They don't really do anything.