You are right, I don't think either that any investor will be happy, allowing his funds to just go like that after his death without pass it on to his next of kin . As at this stage of your life, you are suppose to have gotten someone which you can really trust to pass your inheritance and if you don't,it means you don't trust yourself either or you are not telling yourself the truth,no matter how distance or close you can be to your family members, there most be someone which you will trust and desire to be your next of kin
If you are an investor, and no one knows your private key, or your private key is not backed up in a place where your family members will be able to see it, after your death, then your bitcoin will definitely be useless after your death, because no one will be able to access it. If you don’t trust anyone in your family, and you think no one is worth sharing your private key with, then it’s just better you write it where people will be able to see it, because it’s just going to be painful that after holding bitcoin for some time, none of your family members will be able to access it after your death.
Just as you said it, there should be someone you are going to trust in your family who should know your private key, and in case you don’t want anyone to know it, then it’s just better to have it written in your will, at least your family will be able to see it after your death and will be able to make use of it, and if they want to continue holding it, it’s fine.