Coupling the CSS and JS and HTML isn't a random design choice. It came out of some very useful styleguides for AngularJS (and other guides too, I'm sure). These guidelines suggest grouping the CSS and HTML and JS together when they are related. It makes a lot of sense in larger applications, but maybe not so much for server-rendered static pages.
There are global styles, and there are styles that are relevant only to a particular component. Hoist styles up to a global (or more general) layer whenever you can, but I really appreciate the fact that I know the important styles I need will be in the same file/folder.