Is the horn supposed to not work without the ignition on? I would have though that it should work without the key in, in case of emergencies?

All German cars do that. You can leave the kid/dog in for a moment without fear of waking the entire neighborhood.

Ah ok that makes sense. Thanks.

Also prevents the friends from sounding the horn while you refill the wiper fluid bottle, if you take the key with you, just reminded that. Cheers.