I don't think anyone is too concerned by a few dollars gleaned at a yard sale, they are thinking of pallets of 100's that cartels seem to be able to amass.
Truth is our politicians are for sale and so are the courts and banks, otherwise all this wouldn't be taking place. The laws or lack thereof are exactly what our politicians want otherwise they would change them. Same for tax law as well.
Those pallets are movie stuff now. Drug dealers have always been on the cutting edge of tech. They were early adapters on pagers, cellphone, cash cards and epayment. They have too much at stake.
This stuff is happening because business (legit and not) always wants to move faster. Checks are faster than cash (at least away from the counter). Credit cards are faster than checks. Epayment is faster credit cards. Blockchain will be faster still.