I totally agree that meta titles, descriptions, etc shouldn't be part of the theme. I don't even think it should be a plugin - it should really part of WP functionality.

If you make it part of a theme, then you have to go in a rewrite everything if you change your theme.
If you use a plugin, what if that company decides not to continue developing. The, same problem persists. I should be like it is with Dreamweaver, and part of the functionality. The rest of our SEO (page redirects etc) can be done within the htaccess file.