If it's anything like over here, the guvvvmint decided that we should all ride with our lights on so car drivers might see us better. So, if your lights have to be on compulsorily, you don't need an off switch. That's what we got here, and there's a generation of bikes with no way of turning the lights off.
Interestingly, that stance has been abandoned lately, and now some bikes again have an off switch for the lights, as does my 2003 640A, but not my 2002 GS1150.
That's what I love about guvvmints, today it's good for you, yesterday it was bad for you. What changed? Some senior public servant had nothing to do, so they just think up arbitrary stuff to mimic real activity.