It’s almost as if Lufthansa are admitting they are a terrible airline with awful practices like silently cancelling the return leg of flights if you don’t make the outbound. This happened to me on the way back from Germany, I can’t imagine they still do this but I found them extremely unhelpful and this sort of behaviour reinforces my feeling they think you’re lucky to be travelling with them.
Many airlines do this. Lufthansa did it to me last year. They are usually accommodating if you ask in advance (mine was due to a connecting flight being canceled and driving the last leg was much faster than waiting for the next flight).