I believe the key challenge with process modeling is the unfamiliarity of most business users and even analysts with how to do this and also the lack of availability of easy-to-use tools that are better than just using Word, Visio or PowerPoint.
We have been using the AccuProcess Modeler over the last year and have found this to be a great tool which anyone can use without a lot of training. It includes process modeling, documentation and even process simulation for the as-is and to-be processes. Thanks. - Jenn N.