I think the tide is turning though. Personally, the biggest difficulty I have with using forum-only applications is the difficulty of fully integrating the forum with other Web applications. While a site owner may start out wanting to host only a forum, sooner or later there comes a time when there is need to add more CMS functions than a forum-only application typically provides.

I maintain a site that started out only as a SMF forum but later needed eCommerce functionality (we chose osCommerce) and it now needs blogging functionality. If a site is the sum of all its parts then the site I'm maintaining with all of its non-integrated applications isn't adding up correctly.

While there are work-arounds, third-party bridges, and patches that can be applied to these applications...these mashed sites still rarely achieves "oneness" with all the required applications. And if you are lucky to end up with a fully integrated site via a lot of hacking the core, it only takes for one of those applications to require an upgrade to cause a lot of additional cost in time and money to re-integrate the changes back into your hacked site.

I know a lot of forum-only people that would not be happy with the forum module in Drupal as it is today, however I think we're all headed in the direction Drupal has taken. No, I'm not saying we're all heading to Drupal. What I am saying is the wind is blowing in a new direction where people are wanting more than a forum or a blog or a shopping cart for their site. They're realizing that they need to start using well-rounded CMS applications that provides more than one or two CMS functionalities.