This isn't about file size at all, it is about being able to see as much CSS as possible at one time.

My screen is wide, my editor is wide, my code is fairly wide, but the standard format for CSS is really narrow. Every time I see the vertical format in my editor, easily 80% of the window space is completely empty, and otherwise useless, and 80% of the CSS is not on the screen and I have to page up and down, or search, to find stuff.

This is a workflow optimization that works for me. It might work for others too.