If my graphic artist expected me to go into Adobe every time I needed a new background, I would ask him what his job was.
For me, every time I need a new button, I'm not going to my designer, I'm just copying over the last button. So I need to be able to quickly edit styles, and state functionality, like dropdowns and date pickers. For these types of components, your life will be a living hell if every time you needed to add a style, you were going to a CSS/HTML file. This was how we first worked with Backbone and Handlebars, and it absolutely sucked.
Handlebars is just a general text template language so it was naturaly quite rough. From there one can move to dressing components in the angular style and keep the templates all in one folder and the custom CSS in one file.
My designer and I share the templates folder, I usually add enough attributes for bootstrap to do something or other and then the custom CSS is his and the code is mine.
If we were writing our SPAs for consulting clients it would be essential that the templates and CSS were not compiled so they could go on with them without us and without either paying us to keep a bunch of unstable node tooling able to compile and up to date or feeling like we intentionally snuck a time bomb into the project and are underhanded in seeking hours.