death makes us sad because it's us feeling like we lost something we needed
didn't you cry when you were little, and lost your favourite toy? i'm sure i did. it doesn't necessarily have anything to do with communication with the person. it's not just the fact they died that makes us sad, either.
i'm sure a lot of our parents didn't know anybody from 9/11, but still probably cried when watching the news. it wasn't the fact they were dying, it was how they were and how quickly.