This has generally not been an issue for me, and I code on a 13" laptop most of the time, with no external monitors. Even with all panes but the editor pane closed, there's still the toolbar, tab bar, status bar, and a bit more space taken up, but in practice I just don't find that it matters.

Regardless, "can fit more code on one screen" is not even in my top 10 list of things I look for in my development environment.