"Instead of having us create an administrative interface for updating your web content, you could just install Joomla, WordPress or Drupal and do it yourself."
True. But you're competing with Foursquare and GoDaddy websites for $ 1 / month.
I don't recommend people use those services but in the end that's what you're competing with. Compare that to setting up a website with Drupal.
So you're either severely constrained by a cookie cutter CMS, or completely overwhelmed by a more flexible platform like Drupal. Ultimately I'm not hearing anything convincing about why web development has become obsolete.