Links are fragile and one-sided. You might move the destination. You might edit the title of the destination and want that to show up in the link text. You might want the content, not just the title, to be visible (preferably foldable) from where the link is. You might want to be able to see from the destination what links to it.
In Hugo its actually pretty easy to color code whether a page/destination exists. Optionally you could do up a Wiki using the Media Wiki stuff. Then links are color coded automatically.
