Launchers allow you to have a customised UI, maybe you don’t want to have a Google search bar in you home screen, the default UI doesn’t allow you to change it, a launcher does. What about changing order of icons, maybe you want your icons to shape the capital letter F, with a launcher you can, or you know that real gangstas use IBM Plex Mono instead of Roboto, you ain’t nobody’s bitch, a launcher helps you with that