Personally I never want browser or editor windows to be fullscreened unless I’m working on a tiny screen like on the 12” MacBook Air or maybe 12” Macbook. On anything larger doing that makes for tons of blank space that could be used for other relevant windows or at letting my desktop peek around the edges.

IDEs on the other hand I like having fill my screen because of all their editors and panes, but I still don’t use actual fullscreen but rather option-click the green button which resizes the window to fill the desktop without actually going fullscreen.