Comment by abanana

It should have said maximizing screen height, not space (on desktop not mobile), in these modern days of widescreen monitors. If we have title bars, menu bars, toolbars etc, while using the full screen width, we're peering through a letterbox. (Fixed headers on websites contribute too.) Line length needs to be kept shorter for readability, leading to wasted space at the sides.

Perhaps, if you're not using a sidebar for bookmarks or vertical tabs or whatever, it suggests something ought to have changed in UI design back when widescreen monitors became the norm?