The fact that it's unusual is not relevant. Or it's relevant in that - pretty much by definition - these situations are unusual. It's not okay to violate people's rights merely because "unusual". It's not okay to demand a good story just because "unusual". Instead we get the all too common a reasoning "well, I don't play cards", or "well I have nothing to hide". None of this is relevant. The opposite is true: if you believe in freedom of speech for another example, then it's only for socially uncommon speech that it will matter. In particular, speech that few people would support. If cash is legal, it's only in unusual situation that it has to be particularly protected by the law.