They don't have to. Structuring transactions to avoid reporting laws is also a crime. Periodic withdrawals of $9,999 won't save you.
That non-crimes are made illegal is an indicator of corruption. When crimes are made legal - eg: kidnapping people for doing something that isn't a crime, as this law does, then you have corruption. Enough of that and you have tyranny.
It's easy to remember the difference if you look at it this way: The nazis murdering the jews was a crime, but it was perfectly legal.