Well more for ease of searching/edits when mobile (which i am alot), I will have about 40+ nodes that will all have custom css (about 400 lines per node)
I know one reason I used a second template was for the custom node icons for my MC forum. It was easier to keep up with everything for it in one template dedicated to it. No need to scroll down the screen to find it in EXTRA.css and then enter it there. Most of the other stuff I have is put into just the EXTRA.css.