I wanted to acknowledge that life goes on but that death goes on, too. A person who is dead is a long, long story.
In general, I think people are worried about saying the wrong thing to any grieving person. On a very basic level, I think they're frightened of touching off tears or sorrow, as though someone tearing up at the mention of unhappy news would be the mentioner's fault.
I can't imagine not joking even at the worst of times. And for me, it's sort of automatic.
I have been the person who tries to keep conversation light while talking to someone whose heart has been smashed.
It's an amazing thing to watch a lizard fold a moth into its mouth, like a sword swallower who specialises in umbrellas.