Multiple display. Like app iTerm for example. You can open differents file in the same window! 

You could just open two windows and put them side-by-side.

Split view has more implications than just putting two windows side-by-side.  You may wish to split the same file vertically to simultaneously edit one section while viewing another.  The way Chocolat handles basic splits is fairly intuitive: either explicitly create a horizontal or vertical split from the File menu (same file, two views) or simply select multiple files from the directory listing for different files.

If you're handling splits as completely separate windows there is very little way to control them using keyboard shortcuts without the use of additional software like Moom, and even then management is more of a pain.