I suspect part of the issue is that while you can run a group page on Wordpress/OpenCMS/Drupal, which deals with the content management, they all start to look same-y.

It needs a lot more work to get it looking more like this (which I'm not sure has ever been updated since it was put up there, and it without any CMS software), and people will go for the non-compliant-but-pretty over bare-bones-functional any day.

Just be thankful that nobody(? I hope!) has yet made an entirely flash-driven page.