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.
I don't know about the "silently" part, but this is standard practice for most (all?) airlines.