I had this problem in el salvador, lets point some of the flaws of CryptoCurrencys over physical cash:

1. old people are displaced, I learned how to use lightning by necessity because i forced myself to bring about only 40$ of cash however it was a pain for me because that ended quickly and people would tell me just use an atm, sorry that isn't a good solution and in the end i didn't use it, first atms are kyc and also they steal like 5 to 8% of your value going from bitcoin to fiat, the point of bitcoin is to get rid of Fiat not for a mixed world.
2. the complexity of the whole operation is too complex, both people require to know what is bitcoin, what is a layer 2, what is lightning, how lightning works, that lightning is not as safe as bitcoin base layer, that both persons have smartphones and both have internet, this whole operation looks almost like a ritual and its basically absurd and retarded, now cash is king because you just give the physical paper of 5$ to the other person and they are happy, or you just give 5 coins worth 1$ each and both persons are happy, its elegant, its simple.
3. I hope ctv comes earlier than later, i know the most pure maxis are in their own church we are the first coin, we are the only one decentralized, we are the only ones with no ico etc however that doesn't matter if the competition steps up and eventually wins more users even if they are more centralized garbage, in reality there is space for only one coin and if vitalik manages to fix etherium flaws which i doubt but he will then we will be living in a world where a POS shitcoin controled by jpmorgan dominates the infrastructure of the future of the internet.
4. Lets say some of the original founders of bitcoin, lets give a random number 1000 bitcoins, locks those 1000 bitcoins in a smart contract then we can print physical bitcoin.
5. we need to standarize how qr codes are going to work because sure physical bitcoin can be printed on paper or even wood or metals with 3d printers but all the qr codes ideally look the same so it looks serious and not confusing.
6. money is information, bitcoin is information, qr codes are the physical manifestation of information in a language computers can understand.
7. the qr codes need to be divisible, if you split a qr code in half it no longer works however lets say we print one big qr code with the value of 100,000 satoshis then you should be able to cut the qr code with a scissor and then have 10 smallers qr codes with a value of 10,000 satoshis each.
8. the person with physical bitcoin now its able at any time able to scan and reclaim their satoshis, i suppose every qr code should have an expiration date.

Hopefully someone reads this, i hope i can picture to you how we need to win the war against fiat money, when roman disappeared people hundreds of years later still used the silver denarius, we cannot afford a future where people still use the dollar after the dolar fails we need to displace the dollar with an active force and replace it with a superior form of money.