What if the person holding private key is dead or met with an accident and lost memory or the person gets Alzheimer?
Crypto investment is quite risky and I know the part of we need to always protect ourselves, but we all have loved ones we trust, there are one or two people we can entrust with our crypto funds, in case we die, the thing to do is to educate those persons if they lack crypto knowledge, of how to use the system, what a private key is. etc. That way you'll be preparing them to handle your funds quite well In case something bad happens.
In case of centralised currency there are nominees of the account and ways to get access but, here one has the monopoly on his/her funds. Which is total good and even I like the fact that I am the only one accessing my funds. But, what if any such situation fits in?
The thing with centralized currencies is that when we put up our money in the banks, we are always alert to adding a next of kin who'll inherit out funds if we die, but do not forget that crypto wallets also provides such features in its multi signature wallet which allows you to share your private keys with maybe two of your most trusted family members as well as yourself, that way if you're gone, one of them would not be able to access your funds single-handedly without the other, it adds an extra layer of security.