Is it illegal to have $10,000? If you're referring to financial reporting requirements, the law is just that the bank has to report when you make large deposits (and I think withdrawals as well) it's not a crime, though it is a crime to intentionally deposit multiple amounts less than $10,000 to try and evade the reporting requirements. If you're referring to civil asset forfeiture or something, then I agree work needs to be done to reign in the practice.

It can be illegal doing things even with less than $10K at a time, due to structuring laws. Your business insurance only covers up to $10K cash, so you make deposits of $9500 each week? Cool, enjoy your legal problems.

And you should not have to report the money you carry if you, for instance, travel.