ColdFusion had much more limited exposure to the general world than say PHP. Also, arguably and IMNSHO, ColdFusion was quite bad at a lot of its own features. Custom Tags specifically as the given example, were barely more than duct tape over SSI (Server-Side Includes) and never really had a "proper" Component model or DOM for most (if not all, again IMNSHO) of its history.

(CF is a language on my list of hopes to never see again.)