If you're using a Mac that has a camera housing or 'notch' centered at the top of the screen, like a 14-inch or 16-inch MacBook Pro, hiding the menu bar effectively makes the notch invisible, since the menu bar color turns black in full screen mode, regardless of whether you're using Light or Dark mode. In macOS Monterey, when you take an app fullscreen by clicking the green traffic light icon in the top-left corner of the app window, the menu bar may be hidden from view in order to draw your focus to the window's content.