When we deal with cash, we do not know the source of that cash whether it came from an illegal or legal source one hand before me. I think the Bitcoin hatters are very active to plant the seeds in our head some day we will be in trouble. There will be time when we will not have these centralized exchanges with centralized fiat, there will be a time when we will not have any centralized financial system. Wait for those days.
The fact is that more and more crypto exchanges are implementing some form of monitoring and analysis of the origin of BTC, which in itself would not be bad if it can prevent illegal activities. But it’s also a fact that the average user (and some more advanced ones) can hardly determine if their BTCs have ever been to some blacklisted address.
Cash, however, is something else entirely - unless the banknotes are not marked (serial numbers in a database), anyone can literally use such cash for anything without any fear, so I guess cashiers won’t be CSIs to discover the origin of the money.
The days will come, but how many days will it take - or rather the years for the financial system to become decentralized? I'm not a pessimist by nature, but the system is very firmly rooted and hard to change - at least I haven't heard any serious politicians or bankers talk about it yet.