You can go through each and every physical object I own or even was in contact with, but you won't find any of my passwords
See, for example, the people who know they're going to die and who leave their iPads to their relatives in their wills. Apple doesn't take grants of probate as sufficient legal documents (everyone else does (eg banks)) and insist on a court order.
Leaving a physical trace of my passwords is not only bad practice from security point of view, but quite useless since I know them. Also, my online accounts are useless if I can't use them because I'm dead, so I don't really care if no one can access them anymore. What happens to important things such as banking is already dealt with.
But I think the right solution here would be for Facebook to have a way of handling deceased people, not giving your password to everyone in case of sudden death.