Every so often you hear of someone having cash taken from them during a traffic stop, or search. and at times cash is seized. Then they must prove that it was their money. and in many cases. they did not break any laws.
Lets face it, if you buy a used car from a private owner you need cash, if you buy a older rv, good luck getting a loan, you need cash. planning to spend more in a day then your debt card will dish out, on car repairs, ect. My whole point is to carry 10-20k in cash doesn't mean you broke the law.
Its usually not a every day occurrence, but I'm sure many people find at least once in there life that they are carrying a large amount of cash.