They make bad screw heads but the drivers themselves are useful for so many random odd-jobs that you can basically be guaranteed to find a flathead that’ll fit your screw within a few seconds of searching near basically any tools
Because of that many cheaper companies use flats for their screws, though I almost never see it in anything bigger than the little ass plugs we use in doorknobs and electrical socket covers. Once you go bigger than those it’s usually a Phillips/flat combo, or torx if you’re spending some extra cash