I think it's mostly to avoid the whole mess of having Javascript arbitrarily selecting DOM elements that are declared elsewhere and then manipulating them/cloni

I think it's mostly to avoid the whole mess of having Javascript arbitrarily selecting DOM elements that are declared elsewhere and then manipulating them/cloning them to create some new DOM. If you were creating some DOM/code component intended to act as a black box, it may be conceptually simpler to have the DOM part of it created via code and explicitly referenced by the code. YMMV