Privacy

The problem here is the money itself has no intent. It's not walking towards a bank wearing a mask. And there's no law that says you have to use banks. It's entirely legal to cash out all of your paychecks, keep the money in your mattress, and then go pay for a car in cash. Since the great Depression there are still Americans who distrust the banking system.

To confiscate that money based solely on the fact that it's money should be illegal. It was illegal until the 1980's. Then we convinced ourselves that although we have a right to due process and high standards for searches and seizures of our property; our property itself does not have any rights and can be detained on it's own. That is, they can take your property, without charging you with any crime. They instead charge the money, house, car, etc, with the crime and you are now in the position of proving it's not criminal without any of the court protections you would have if you were charged. No jury, no free lawyer, and no assumption of innocence for the state to overcome.

If that sounds like something that could be abused, it absolutely has been. Cities have used it to clear land for development without paying for it. Some small towns are notorious for taking any bundles of cash they can from people passing through.