I stumbled upon an article by Den Delimarsky on What is a ContentPresenter? which says:
In WPF there is an element called ContentPresenter, that is often used inside control templates, as well as inside the root application markup.
I don't understand the "inside the root application markup" part, because I thought that ContentPresenter can only used inside of a ControlTemplate.
The role of the ContentPresenter is quite clear when used in a ControlTemplate, but what are the valid reasons to use ContentPresenter outside of a template's markup?