Both cash and crypto have their downsides when it comes to money laundering. A non-tech savy person might not trust their crypto transactions to remain anonymous or their funds to be safe, because at the end of the day the only way you can be sure of that is if you read and understood the code. For that kind of person the weight of cash is the lesser issue. I've been told that decades ago my dad's uncle would go on trips to Switzerland with bags full of cash.