I know it's a noob question, but why would you want to do anything but texture a mesh in the 0-1 UV space? For instance, say I wanted a mossy tree. Couldn't I just unwrap the tree in the 0-1 UV space and uniquely texture it getting the same result as if I used a composite of a tiling bark/moss texture? I'd use less textures this way. It makes sense to me that you would want to do nothing but texture in a 0-1 UV space, but I'm sure there's a reason why it's not always the go to process. No matter what you're texturing you still have to unwrap it in some form, so I'm just wondering what the benefits are to expanding the unwrap outside the UV square.