Dude, why can’t I add a Workflow or Form Library to Enterprise MOSS?

Because in a publishing site some features are not activated by default. Activating the features below adds back your functionality you are used to on a collaboration site. I had this issue on two separate projects this week!

Ensure that the following features are enabled (on the site and the site collection):

1. Office SharePoint Server Enterprise Site features
2. Team Collaboration Lists
3. Office SharePoint Server Standard Site features

From: http://www.williamkent.net/archive/2008/06/09/configuring-sharepoint-for-use-with-infopath-and-forms-server.aspx