It's practically impossible to get meaningful quantities of it without having a SAR or CTR filed against you. Denominations are small so having a large amount is visible, risky, bulky and inefficient. Not to mention hard to explain away. And it's practically impossible to deposit meaningful quantities of it without having a SAR or CTR filed. The whole modern financial system is designed to catch criminals using cash.
Cash does a good job of threading the needle, taking into consideration the need for individuals to have a peer-to-peer, anonymous, offline decentralized currency while also taking into consideration regulatory and compliance needs.
I've nothing against cash, it has it's place, and no need to put words in my mouth.