There is no problem with value changing tomorrow as this is a potential problem with any new payment methodologies. Adoption does not appear magically overnight. The US Dollar is velocity stable due to its wide spread use and being propped up by the equivalent of a bunch of duct tape and bailing wire.
There was a guy on reddit who had all of his DOGE and BTC lifted right off his computer. He was using strong, auto-generated passwords stored in a password manager, so he was not even typing in passwords that a keylogger could intercept. Presumably the attacker had a backdoor into his system, watched him work, and just transferred out the funds when he wasn't at his desk. Poof - all gone, with more or less proper security measures in place and no clear sign of an intruder other than the missing money. Several other people reported similar events in that thread.
These are still major problems for mass adoption of crypto, completely setting aside the massive cases of fraudulent pools, online wallets, exchanges, etc., etc. There are many subtle problems that are difficult to diagnose and cure that come with a technological solution like bitcoin, that paper money simply does not have.
When he died, my grand-aunt, who always thought he was being silly, went out in the woods and retrieved all the jars.
The cash had rotted and deteriorated to the point that it was unspendable.
However, she was able to work with the US Treasury to sort through the remains and identify the bills and replace them with new currency.
There's not really a bitcoin lesson here, just some family lore that seemed relevant. :-)
These days spending old banknotes is problematic, even if they're in perfect condition.
Some people love gold, some people hate it, but everyone agrees it's the only thing that really has zero counterparty risk.
Not that I think this is the ne plus ultra of security, but since having a digital wallet doesn't obviate the existence of valuable physical documents (eg passports, title deeds) you might still want to use a safe to protect against fire, burglary, and so on.
One distinct benefit of a physical store is that removal or tampering are more obvious.
The chances of everyone doing this and being comfortable with it is pretty low though. We need brain storage medium.
In both cases, there is one physical good which, when stolen, deprives you off the money. With cash, it's the physical notes. With Bitcoin, it's the private keys in the wallet (or private key to unlock the wallet's private keys). Making backups of the keys can protect against accidental data loss, but not against theft, as it increases attack surface (i.e. number of locations where the same money can be stolen from).
There is still an advantage here favoring Bitcoin, though: if the key is stolen and you know this, you still have a chance to preserve the wallet's holdings: just generate new keys (addresses) and broadcast a transaction of all the wallet's money to those addresses. If you can get the message to the network's nodes faster than the attacker, the money will be "signed away" before they can use it, and such attempts will be rejected as double-spends.
There is no corresponding feature for physical cash.
While you could construct a procedure to spend cash remotely without one powerful intermediate, this property is just built into to *coins, and it is simply how they work.