Allow creation of simple dialog box through code only, without having to define a template for it, as this is cumbersome for very simple dialogs. Examples:
MessageBox.Show("Title", "This is a message");
MessageBox.Show("Title", "This is a message", MessageBoxKind.Info);
MessageBox.Show("Title", "This is a message", MessageBoxOptions);
Where MessageBoxOptions could be an object defining Width, Height, Buttons, Animation, etc.
Now it's possible to define a template and call it from other components, but that's an unnecessary work to do, as this feature is essential in any programming environment that faces user interaction.