“the bank may know that you withdrew cash, but what happens with that cash and where you spent it is entirely up to you and it’s very hard to track it.”
20 year US banking veteran here, in the US an insane amount of time and effort is put into cold tracing cash supply movements. Like, violent stalker ex pinning down your every movement, going through your garbage, zero potential return on investment kinda effort.
It’s commonly used in drug cases. But any benefit is dwarfed by the cost of maintaining all the required infrastructure. And, yes, the system is extremely vulnerable to data poisoning