I don't quite understand - what is the actual purpose of being able to push a new version of iOS while locked? Apple don't seem to use this - people stick to wh

I don't quite understand - what is the actual purpose of being able to push a new version of iOS while locked? Apple don't seem to use this - people stick to whichever version they're comfortable with on old devices and accept whatever limitations.. so why does the functionality even exist? Even with the restriction of being plugged in, outside of Apple who needs to push iOS versions at tethered devices and will be hindered too badly by having to unlock them first?