What I mean by that is that unlike fiat it isn't just dropped to the ground and someone else can pick it up and use it. Or even when you are deceased it's not just a case of signing over the funds to someone else. They have to have the private key available to access the funds.
Make sense. You were talking about physical existence.
We are into a time where currency don't need to be physically exist. Think about online banking system, paypal and kind of payment processing system - shopping online does not require touching the currency. Currency are just some virtual digits and numbers.
In future there will be time when we will completely deny (perhaps will never need) a physical currency. Any financial transaction? Just swipe your mobile device or a contact less device or kind of things and trade done!