>Providing space [...] around [...] your content can increase the appeal of your page. Just like black bars when the aspect ratio of a movie doesn't match that

>Providing space [...] around [...] your content can increase the appeal of your page. Just like black bars when the aspect ratio of a movie doesn't match that of my monitor increase the appeal of said movie. I find margins on mobile pages a complete waste of horizontal space. My device screen is only 6cm wide and already surrounded by plenty of space in my field of vision. Why make it even narrower?