Just look at
Schumacher's accident, which is potentially a life changing event for him and his family. Having his key only in his brain may mean his
BTC are lost for ever. But having a plain copy in the safe is a different story.
If anything, that should provide my scheming wife/kids with more motivation to keep me alive because if I die they'll get nothing.
If it's in the family safe however ...
/not married.