As far as I understand, a person initially does not want to trust his money to anyone, friend or family. He wants them to be able, even theoretically, to receive money only after his death, and not earlier. And here big problems are possible, because let's say that a person does not trust anyone, although, I would probably suggest then, a bank cell.
It is still possible, can leave an inheritance by just putting small information that only our friend knows and the half information for our family in which when combined together, could potentially unlock the funds that we secured. It is not necessary to provide the password, maybe just give some hints, we'll not give out anything while we live, the idea is to preserve it till we die so our family will benefit from it, might as well provide a small credit to our friends.
But as the cryptocurrency era is currently expanding and develops I think pretty soon, there will be services that will offer this bitcoin inheritance system.
Maybe it is good idea having handbook where your account is listed with the password or private keys and leave it on your locker where your family have access when you live this world. While you are alive,.your family knows about your transactions and crypto even they do not involve on it which give them hint that their inheritance has something to do with it.